diff --git a/admin/settings_mail.php b/admin/settings_mail.php
index f66f2b8e..806119ec 100644
--- a/admin/settings_mail.php
+++ b/admin/settings_mail.php
@@ -1,601 +1,524 @@
 <?php
 require_once "includes/inc_all_admin.php";
- ?>
 
-    <div class="card card-dark">
-        <div class="card-header py-3">
-            <h3 class="card-title"><i class="fas fa-fw fa-envelope mr-2"></i>SMTP Mail Settings <small>(For Sending Email)</small></h3>
-        </div>
-        <div class="card-body">
-            <form action="post.php" method="post" autocomplete="off">
-                <input type="hidden" name="csrf_token" value="<?php echo $_SESSION['csrf_token'] ?>">
+// ---- Tiny status dot for tab labels ----------------------------------------
+function mail_status_dot($on) {
+    return $on
+        ? '<i class="fas fa-circle text-success ml-2" style="font-size:.5rem;vertical-align:middle;" title="Configured"></i>'
+        : '<i class="far fa-circle text-muted ml-2" style="font-size:.5rem;vertical-align:middle;" title="Not configured"></i>';
+}
 
-                <!-- SMTP Provider -->
-                <div class="form-group">
-                    <label>SMTP Provider</label>
-                    <div class="input-group">
-                        <div class="input-group-prepend">
-                            <span class="input-group-text"><i class="fa fa-fw fa-cloud"></i></span>
-                        </div>
-                        <select class="form-control" name="config_smtp_provider" id="config_smtp_provider">
-                            <option value="" <?php if(empty($config_smtp_provider)) { echo 'selected'; } ?>>None (Disabled)</option>
-                            <option value="standard_smtp" <?php if($config_smtp_provider === 'standard_smtp') { echo 'selected'; } ?>>Standard SMTP (Username/Password)</option>
-                            <option value="google_oauth" <?php if($config_smtp_provider === 'google_oauth') { echo 'selected'; } ?>>Google Workspace (OAuth)</option>
-                            <option value="microsoft_oauth" <?php if($config_smtp_provider === 'microsoft_oauth') { echo 'selected'; } ?>>Microsoft 365 (OAuth)</option>
-                        </select>
-                    </div>
-                    <small class="text-secondary d-block mt-1" id="smtp_provider_hint">
-                        Choose your SMTP provider. OAuth options ignore the SMTP password here.
-                    </small>
-                </div>
+$smtp_on = !empty($config_smtp_provider);
+$imap_on = !empty($config_imap_provider);
+$oauth_needed = in_array($config_smtp_provider, ['google_oauth', 'microsoft_oauth'], true)
+             || in_array($config_imap_provider, ['google_oauth', 'microsoft_oauth'], true);
 
+// ---- OAuth callback URI (for Entra App Registration) ------------------------
+if (defined('BASE_URL') && !empty(BASE_URL)) {
+    $mail_oauth_callback_uri = rtrim((string) BASE_URL, '/') . '/admin/oauth_microsoft_mail_callback.php';
+} else {
+    $mail_oauth_callback_uri = 'https://' . rtrim((string) $config_base_url, '/') . '/admin/oauth_microsoft_mail_callback.php';
+}
 
-                <!-- Standard SMTP fields (show only for standard_smtp) -->
-                <div id="smtp_standard_fields">
-                    <div class="form-group">
-                        <label>SMTP Host</label>
-                        <div class="input-group">
-                            <div class="input-group-prepend">
-                                <span class="input-group-text"><i class="fa fa-fw fa-server"></i></span>
-                            </div>
-                            <input type="text" class="form-control" name="config_smtp_host" placeholder="Mail Server Address" value="<?php echo nullable_htmlentities($config_smtp_host); ?>" required>
-                        </div>
-                    </div>
+// ---- Readiness checks (drive the Tests tab) --------------------------------
+$smtp_standard_ready = !empty($config_smtp_host) && !empty($config_smtp_port)
+    && !empty($config_mail_from_email) && !empty($config_mail_from_name);
+
+$smtp_oauth_ready = in_array($config_smtp_provider, ['google_oauth', 'microsoft_oauth'], true)
+    && !empty($config_mail_from_email) && !empty($config_mail_from_name)
+    && !empty($config_mail_oauth_client_id) && !empty($config_mail_oauth_client_secret)
+    && !empty($config_mail_oauth_refresh_token)
+    && ($config_smtp_provider !== 'microsoft_oauth' || !empty($config_mail_oauth_tenant_id));
+
+$imap_standard_ready = !empty($config_imap_username) && !empty($config_imap_password)
+    && !empty($config_imap_host) && !empty($config_imap_port);
+
+$imap_oauth_ready = in_array($config_imap_provider, ['google_oauth', 'microsoft_oauth'], true)
+    && !empty($config_imap_username)
+    && !empty($config_mail_oauth_client_id) && !empty($config_mail_oauth_client_secret)
+    && !empty($config_mail_oauth_refresh_token)
+    && ($config_imap_provider !== 'microsoft_oauth' || !empty($config_mail_oauth_tenant_id));
+
+$oauth_provider_for_test = '';
+if (in_array($config_imap_provider, ['google_oauth', 'microsoft_oauth'], true)) {
+    $oauth_provider_for_test = $config_imap_provider;
+} elseif (in_array($config_smtp_provider, ['google_oauth', 'microsoft_oauth'], true)) {
+    $oauth_provider_for_test = $config_smtp_provider;
+}
+
+$oauth_has_required_fields = !empty($oauth_provider_for_test)
+    && !empty($config_mail_oauth_client_id) && !empty($config_mail_oauth_client_secret)
+    && !empty($config_mail_oauth_refresh_token)
+    && ($oauth_provider_for_test !== 'microsoft_oauth' || !empty($config_mail_oauth_tenant_id));
+
+$send_ready = $smtp_standard_ready || $smtp_oauth_ready;
+$imap_ready = $imap_standard_ready || $imap_oauth_ready;
+?>
+
+<div class="card card-dark">
+    <div class="card-header py-3">
+        <h3 class="card-title"><i class="fas fa-fw fa-envelope mr-2"></i>Mail Configuration</h3>
+    </div>
+    <div class="card-body">
+
+        <ul class="nav nav-tabs" id="mailTabs" role="tablist">
+            <li class="nav-item">
+                <a class="nav-link active" href="#tab-smtp" data-target="#tab-smtp">
+                    <i class="fas fa-fw fa-paper-plane mr-1"></i>Sending<?php echo mail_status_dot($smtp_on); ?>
+                </a>
+            </li>
+            <li class="nav-item">
+                <a class="nav-link" href="#tab-imap" data-target="#tab-imap">
+                    <i class="fas fa-fw fa-inbox mr-1"></i>Receiving<?php echo mail_status_dot($imap_on); ?>
+                </a>
+            </li>
+            <li class="nav-item" id="tabitem-oauth" style="<?php echo $oauth_needed ? '' : 'display:none;'; ?>">
+                <a class="nav-link" href="#tab-oauth" data-target="#tab-oauth">
+                    <i class="fas fa-fw fa-key mr-1"></i>OAuth
+                </a>
+            </li>
+            <li class="nav-item">
+                <a class="nav-link" href="#tab-from" data-target="#tab-from">
+                    <i class="fas fa-fw fa-at mr-1"></i>From Addresses
+                </a>
+            </li>
+            <li class="nav-item">
+                <a class="nav-link" href="#tab-tests" data-target="#tab-tests">
+                    <i class="fas fa-fw fa-vial mr-1"></i>Tests
+                </a>
+            </li>
+        </ul>
+
+        <div class="tab-content pt-4">
+
+            <!-- ============================ SENDING / SMTP ============================ -->
+            <div class="tab-pane fade show active" id="tab-smtp" role="tabpanel">
+                <form action="post.php" method="post" autocomplete="off">
+                    <input type="hidden" name="csrf_token" value="<?php echo $_SESSION['csrf_token']; ?>">
 
                     <div class="form-group">
-                        <label>SMTP Port</label>
+                        <label>SMTP Provider <small class="text-muted">— outbound</small></label>
                         <div class="input-group">
-                            <div class="input-group-prepend">
-                                <span class="input-group-text"><i class="fa fa-fw fa-plug"></i></span>
-                            </div>
-                            <input type="number" min="0" class="form-control" name="config_smtp_port" placeholder="Mail Server Port Number" value="<?php echo intval($config_smtp_port); ?>" required>
-                        </div>
-                    </div>
-
-                    <div class="form-group">
-                        <label>Encryption</label>
-                        <div class="input-group">
-                            <div class="input-group-prepend">
-                                <span class="input-group-text"><i class="fa fa-fw fa-lock"></i></span>
-                            </div>
-                            <select class="form-control" name="config_smtp_encryption">
-                                <option value=''>None</option>
-                                <option <?php if ($config_smtp_encryption == 'tls') { echo "selected"; } ?> value="tls">TLS</option>
-                                <option <?php if ($config_smtp_encryption == 'ssl') { echo "selected"; } ?> value="ssl">SSL</option>
+                            <div class="input-group-prepend"><span class="input-group-text"><i class="fa fa-fw fa-cloud"></i></span></div>
+                            <select class="form-control" name="config_smtp_provider" id="config_smtp_provider">
+                                <option value="" <?php if (empty($config_smtp_provider)) { echo 'selected'; } ?>>None (Disabled)</option>
+                                <option value="standard_smtp" <?php if ($config_smtp_provider === 'standard_smtp') { echo 'selected'; } ?>>Standard SMTP (Username/Password)</option>
+                                <option value="google_oauth" <?php if ($config_smtp_provider === 'google_oauth') { echo 'selected'; } ?>>Google Workspace (OAuth)</option>
+                                <option value="microsoft_oauth" <?php if ($config_smtp_provider === 'microsoft_oauth') { echo 'selected'; } ?>>Microsoft 365 (OAuth)</option>
                             </select>
                         </div>
+                        <small class="form-text text-muted" id="smtp_provider_hint">Choose your outbound mail provider.</small>
                     </div>
 
-                    <div class="form-group">
-                        <label>SMTP Username</label>
-                        <div class="input-group">
-                            <div class="input-group-prepend">
-                                <span class="input-group-text"><i class="fa fa-fw fa-user"></i></span>
+                    <div id="smtp_conn_fields">
+                        <div class="form-row">
+                            <div class="form-group col-md-6">
+                                <label>SMTP Host</label>
+                                <div class="input-group">
+                                    <div class="input-group-prepend"><span class="input-group-text"><i class="fa fa-fw fa-server"></i></span></div>
+                                    <input type="text" class="form-control" name="config_smtp_host" placeholder="mail.yourcompany.com" value="<?php echo nullable_htmlentities($config_smtp_host); ?>" required>
+                                </div>
+                            </div>
+                            <div class="form-group col-md-3">
+                                <label>Port</label>
+                                <div class="input-group">
+                                    <div class="input-group-prepend"><span class="input-group-text"><i class="fa fa-fw fa-plug"></i></span></div>
+                                    <input type="number" min="0" class="form-control" name="config_smtp_port" placeholder="587" value="<?php echo intval($config_smtp_port); ?>" required>
+                                </div>
+                            </div>
+                            <div class="form-group col-md-3">
+                                <label>Encryption</label>
+                                <div class="input-group">
+                                    <div class="input-group-prepend"><span class="input-group-text"><i class="fa fa-fw fa-lock"></i></span></div>
+                                    <select class="form-control" name="config_smtp_encryption">
+                                        <option value="">None</option>
+                                        <option <?php if ($config_smtp_encryption == 'tls') { echo "selected"; } ?> value="tls">TLS</option>
+                                        <option <?php if ($config_smtp_encryption == 'ssl') { echo "selected"; } ?> value="ssl">SSL</option>
+                                    </select>
+                                </div>
                             </div>
-                            <input type="text" class="form-control" name="config_smtp_username" placeholder="Username (Leave blank if no auth is required)" value="<?php echo nullable_htmlentities($config_smtp_username); ?>">
                         </div>
                     </div>
 
-                    <div class="form-group" id="smtp_password_group">
-                        <div class="form-group">
+                    <div class="form-row">
+                        <div class="form-group col-md-6" id="smtp_user_group">
+                            <label id="smtp_user_label">SMTP Username</label>
+                            <div class="input-group">
+                                <div class="input-group-prepend"><span class="input-group-text"><i class="fa fa-fw fa-user"></i></span></div>
+                                <input type="text" class="form-control" name="config_smtp_username" placeholder="Username" value="<?php echo nullable_htmlentities($config_smtp_username); ?>">
+                            </div>
+                            <small class="form-text text-muted" id="smtp_user_hint">Leave blank if no authentication is required.</small>
+                        </div>
+                        <div class="form-group col-md-6" id="smtp_pass_group">
                             <label>SMTP Password</label>
                             <div class="input-group">
-                                <div class="input-group-prepend">
-                                    <span class="input-group-text"><i class="fa fa-fw fa-key"></i></span>
-                                </div>
-                                <input type="password" class="form-control" data-toggle="password" name="config_smtp_password" placeholder="Password (Leave blank if no auth is required)" value="<?php echo nullable_htmlentities($config_smtp_password); ?>" autocomplete="new-password">
-                                <div class="input-group-append">
-                                    <span class="input-group-text"><i class="fa fa-fw fa-eye"></i></span>
-                                </div>
+                                <div class="input-group-prepend"><span class="input-group-text"><i class="fa fa-fw fa-key"></i></span></div>
+                                <input type="password" class="form-control" data-toggle="password" name="config_smtp_password" placeholder="Password" value="<?php echo nullable_htmlentities($config_smtp_password); ?>" autocomplete="new-password">
+                                <div class="input-group-append"><span class="input-group-text"><i class="fa fa-fw fa-eye"></i></span></div>
                             </div>
                         </div>
                     </div>
 
-                </div>
-
-                <!-- OAuth account (licensed user) - shown only for OAuth SMTP providers -->
-                <div id="smtp_oauth_account" style="display:none;">
-                    <div class="form-group">
-                        <label>OAuth Account / Licensed User Email</label>
-                        <div class="input-group">
-                            <div class="input-group-prepend">
-                                <span class="input-group-text"><i class="fa fa-fw fa-user-shield"></i></span>
-                            </div>
-                            <input type="text" class="form-control" name="config_smtp_username" placeholder="licensed.user@yourcompany.com" value="<?php echo nullable_htmlentities($config_smtp_username); ?>">
-                        </div>
-                        <small class="text-secondary d-block mt-1">
-                            The licensed user that completed the OAuth connect flow — <strong>not</strong> the From / shared-mailbox address. This becomes the <code>user=</code> identity in the XOAUTH2 string and must match the account the refresh token was issued for, or Microsoft/Google returns <code>535 5.7.3 Authentication unsuccessful</code>.
-                        </small>
-                    </div>
-                </div>
-
-                <hr>
-
-                <button type="submit" name="edit_mail_smtp_settings" class="btn btn-primary text-bold"><i class="fas fa-check mr-2"></i>Save</button>
-
-            </form>
-        </div>
-    </div>
-
-    <div class="card card-dark">
-        <div class="card-header py-3">
-            <h3 class="card-title"><i class="fas fa-fw fa-envelope mr-2"></i>IMAP Mail Settings <small>(For Monitoring Ticket Inbox)</small></h3>
-        </div>
-        <div class="card-body">
-            <form action="post.php" method="post" autocomplete="off">
-                <input type="hidden" name="csrf_token" value="<?php echo $_SESSION['csrf_token'] ?>">
-
-                <div class="form-group">
-                    <label>IMAP Provider</label>
-                    <div class="input-group">
-                        <div class="input-group-prepend">
-                            <span class="input-group-text"><i class="fa fa-fw fa-cloud"></i></span>
-                        </div>
-                        <select class="form-control" name="config_imap_provider" id="config_imap_provider">
-                            <option value="" <?php if(empty($config_imap_provider)) { echo 'selected'; } ?>>None (Disabled)</option>
-                            <option value="standard_imap" <?php if($config_imap_provider === 'standard_imap') { echo 'selected'; } ?>>Standard IMAP (Username/Password)</option>
-                            <option value="google_oauth" <?php if($config_imap_provider === 'google_oauth') { echo 'selected'; } ?>>Google Workspace (OAuth)</option>
-                            <option value="microsoft_oauth" <?php if($config_imap_provider === 'microsoft_oauth') { echo 'selected'; } ?>>Microsoft 365 (OAuth)</option>
-                        </select>
-                    </div>
-                    <small class="text-secondary d-block mt-1" id="imap_provider_hint">
-                    Select your mailbox provider. OAuth options ignore the IMAP password here.
-                    </small>
-                </div>
-                <div id="standard_fields" style="display:none;">
-                    <div class="form-group">
-                        <label>IMAP Host</label>
-                        <div class="input-group">
-                            <div class="input-group-prepend">
-                                <span class="input-group-text"><i class="fa fa-fw fa-server"></i></span>
-                            </div>
-                            <input type="text" class="form-control" name="config_imap_host" placeholder="Incoming Mail Server Address (for email to ticket parsing)" value="<?php echo nullable_htmlentities($config_imap_host); ?>">
+                    <div class="alert alert-info" id="smtp_oauth_pointer" style="display:none;">
+                        <div class="d-flex align-items-center justify-content-between">
+                            <span><i class="fas fa-fw fa-info-circle mr-2"></i>This provider uses OAuth — the password is ignored. Enter app credentials in the OAuth tab.</span>
+                            <button type="button" class="btn btn-sm btn-outline-primary goto-oauth ml-3 text-nowrap"><i class="fas fa-fw fa-key mr-1"></i>Open OAuth</button>
                         </div>
                     </div>
 
+                    <hr>
+                    <button type="submit" name="edit_mail_smtp_settings" class="btn btn-primary text-bold"><i class="fas fa-check mr-2"></i>Save Sending Settings</button>
+                </form>
+            </div>
+
+            <!-- ============================ RECEIVING / IMAP ============================ -->
+            <div class="tab-pane fade" id="tab-imap" role="tabpanel">
+                <form action="post.php" method="post" autocomplete="off">
+                    <input type="hidden" name="csrf_token" value="<?php echo $_SESSION['csrf_token']; ?>">
+
                     <div class="form-group">
-                        <label>IMAP Port</label>
+                        <label>IMAP Provider <small class="text-muted">— inbound ticket inbox</small></label>
                         <div class="input-group">
-                            <div class="input-group-prepend">
-                                <span class="input-group-text"><i class="fa fa-fw fa-plug"></i></span>
-                            </div>
-                            <input type="number" min="0" class="form-control" name="config_imap_port" placeholder="Incoming Mail Server Port Number (993)" value="<?php echo intval($config_imap_port); ?>">
-                        </div>
-                    </div>
-
-                    <div class="form-group">
-                        <label>IMAP Encryption</label>
-                        <div class="input-group">
-                            <div class="input-group-prepend">
-                                <span class="input-group-text"><i class="fa fa-fw fa-lock"></i></span>
-                            </div>
-                            <select class="form-control" name="config_imap_encryption">
-                                <option value=''>None</option>
-                                <option <?php if ($config_imap_encryption == 'tls') { echo "selected"; } ?> value="tls">TLS</option>
-                                <option <?php if ($config_imap_encryption == 'ssl') { echo "selected"; } ?> value="ssl">SSL</option>
+                            <div class="input-group-prepend"><span class="input-group-text"><i class="fa fa-fw fa-cloud"></i></span></div>
+                            <select class="form-control" name="config_imap_provider" id="config_imap_provider">
+                                <option value="" <?php if (empty($config_imap_provider)) { echo 'selected'; } ?>>None (Disabled)</option>
+                                <option value="standard_imap" <?php if ($config_imap_provider === 'standard_imap') { echo 'selected'; } ?>>Standard IMAP (Username/Password)</option>
+                                <option value="google_oauth" <?php if ($config_imap_provider === 'google_oauth') { echo 'selected'; } ?>>Google Workspace (OAuth)</option>
+                                <option value="microsoft_oauth" <?php if ($config_imap_provider === 'microsoft_oauth') { echo 'selected'; } ?>>Microsoft 365 (OAuth)</option>
                             </select>
                         </div>
+                        <small class="form-text text-muted" id="imap_provider_hint">Select your mailbox provider.</small>
                     </div>
-                </div>
 
-                <div class='form-group'>
-                    <label>IMAP Username</label>
-                    <div class='input-group'>
-                        <div class='input-group-prepend'>
-                            <span class='input-group-text'><i class='fa fa-fw fa-user'></i></span>
-                        </div>
-                        <input type='text' class='form-control' name='config_imap_username' placeholder='Username (email address)' value="<?php echo nullable_htmlentities($config_imap_username); ?>" required>
-                    </div>
-                </div>
-
-                <div class='form-group' id="imap_password_group">
-                    <label>IMAP Password</label>
-                    <div class='input-group'>
-                        <div class='input-group-prepend'>
-                            <span class='input-group-text'><i class='fa fa-fw fa-key'></i></span>
-                        </div>
-                        <input type='password' class='form-control' data-toggle='password' name='config_imap_password' placeholder='Password (not used for OAuth)' value="<?php echo nullable_htmlentities($config_imap_password); ?>" autocomplete='new-password'>
-                        <div class='input-group-append'>
-                            <span class='input-group-text'><i class='fa fa-fw fa-eye'></i></span>
+                    <div id="imap_conn_fields">
+                        <div class="form-row">
+                            <div class="form-group col-md-6">
+                                <label>IMAP Host</label>
+                                <div class="input-group">
+                                    <div class="input-group-prepend"><span class="input-group-text"><i class="fa fa-fw fa-server"></i></span></div>
+                                    <input type="text" class="form-control" name="config_imap_host" placeholder="imap.yourcompany.com" value="<?php echo nullable_htmlentities($config_imap_host); ?>">
+                                </div>
+                            </div>
+                            <div class="form-group col-md-3">
+                                <label>Port</label>
+                                <div class="input-group">
+                                    <div class="input-group-prepend"><span class="input-group-text"><i class="fa fa-fw fa-plug"></i></span></div>
+                                    <input type="number" min="0" class="form-control" name="config_imap_port" placeholder="993" value="<?php echo intval($config_imap_port); ?>">
+                                </div>
+                            </div>
+                            <div class="form-group col-md-3">
+                                <label>Encryption</label>
+                                <div class="input-group">
+                                    <div class="input-group-prepend"><span class="input-group-text"><i class="fa fa-fw fa-lock"></i></span></div>
+                                    <select class="form-control" name="config_imap_encryption">
+                                        <option value="">None</option>
+                                        <option <?php if ($config_imap_encryption == 'tls') { echo "selected"; } ?> value="tls">TLS</option>
+                                        <option <?php if ($config_imap_encryption == 'ssl') { echo "selected"; } ?> value="ssl">SSL</option>
+                                    </select>
+                                </div>
+                            </div>
+                        </div>
+                    </div>
+
+                    <div class="form-row">
+                        <div class="form-group col-md-6" id="imap_user_group">
+                            <label id="imap_user_label">IMAP Username</label>
+                            <div class="input-group">
+                                <div class="input-group-prepend"><span class="input-group-text"><i class="fa fa-fw fa-user"></i></span></div>
+                                <input type="text" class="form-control" name="config_imap_username" placeholder="tickets@yourcompany.com" value="<?php echo nullable_htmlentities($config_imap_username); ?>" required>
+                            </div>
+                            <small class="form-text text-muted" id="imap_user_hint">The mailbox address to monitor for incoming tickets.</small>
+                        </div>
+                        <div class="form-group col-md-6" id="imap_pass_group">
+                            <label>IMAP Password</label>
+                            <div class="input-group">
+                                <div class="input-group-prepend"><span class="input-group-text"><i class="fa fa-fw fa-key"></i></span></div>
+                                <input type="password" class="form-control" data-toggle="password" name="config_imap_password" placeholder="Password" value="<?php echo nullable_htmlentities($config_imap_password); ?>" autocomplete="new-password">
+                                <div class="input-group-append"><span class="input-group-text"><i class="fa fa-fw fa-eye"></i></span></div>
+                            </div>
+                        </div>
+                    </div>
+
+                    <div class="alert alert-info" id="imap_oauth_pointer" style="display:none;">
+                        <div class="d-flex align-items-center justify-content-between">
+                            <span><i class="fas fa-fw fa-info-circle mr-2"></i>This provider uses OAuth — the password is ignored. Enter app credentials in the OAuth tab.</span>
+                            <button type="button" class="btn btn-sm btn-outline-primary goto-oauth ml-3 text-nowrap"><i class="fas fa-fw fa-key mr-1"></i>Open OAuth</button>
                         </div>
                     </div>
-                </div>
 
-                <!-- OAuth shared fields (show for google_oauth / microsoft_oauth) -->
-                <div id="smtp_oauth_fields" style="display:none;">
                     <hr>
-                    <h5 class="mb-2">OAuth Settings (shared for IMAP & SMTP)</h5>
-                    <p class="text-secondary" id="oauth_hint">
-                        Configure OAuth credentials for the selected provider.
-                    </p>
+                    <button type="submit" name="edit_mail_imap_settings" class="btn btn-primary text-bold"><i class="fas fa-check mr-2"></i>Save Receiving Settings</button>
+                </form>
+            </div>
 
-                    <div class="form-group">
-                        <label>OAuth Client ID</label>
-                        <div class="input-group">
-                            <div class="input-group-prepend"><span class="input-group-text"><i class="fa fa-fw fa-id-badge"></i></span></div>
-                            <input type="text" class="form-control" name="config_mail_oauth_client_id"
-                                   value="<?php echo nullable_htmlentities($config_mail_oauth_client_id ?? ''); ?>">
-                        </div>
+            <!-- ============================ OAUTH ============================ -->
+            <div class="tab-pane fade" id="tab-oauth" role="tabpanel">
+                <form action="post.php" method="post" autocomplete="off">
+                    <input type="hidden" name="csrf_token" value="<?php echo $_SESSION['csrf_token']; ?>">
+
+                    <div class="alert alert-secondary" id="oauth_hint">
+                        <i class="fas fa-fw fa-info-circle mr-2"></i>These credentials are shared by any Sending or Receiving provider set to Google / Microsoft OAuth.
                     </div>
 
-                    <div class="form-group">
-                        <label>OAuth Client Secret</label>
-                        <div class="input-group">
-                            <div class="input-group-prepend"><span class="input-group-text"><i class="fa fa-fw fa-key"></i></span></div>
-                            <input type="password" class="form-control" data-toggle="password" name="config_mail_oauth_client_secret"
-                                   value="<?php echo nullable_htmlentities($config_mail_oauth_client_secret ?? ''); ?>" autocomplete="new-password">
-                            <div class="input-group-append"><span class="input-group-text"><i class="fa fa-fw fa-eye"></i></span></div>
+                    <div class="form-row">
+                        <div class="form-group col-md-6">
+                            <label>OAuth Client ID</label>
+                            <div class="input-group">
+                                <div class="input-group-prepend"><span class="input-group-text"><i class="fa fa-fw fa-id-badge"></i></span></div>
+                                <input type="text" class="form-control" name="config_mail_oauth_client_id" value="<?php echo nullable_htmlentities($config_mail_oauth_client_id ?? ''); ?>">
+                            </div>
+                        </div>
+                        <div class="form-group col-md-6">
+                            <label>OAuth Client Secret</label>
+                            <div class="input-group">
+                                <div class="input-group-prepend"><span class="input-group-text"><i class="fa fa-fw fa-key"></i></span></div>
+                                <input type="password" class="form-control" data-toggle="password" name="config_mail_oauth_client_secret" value="<?php echo nullable_htmlentities($config_mail_oauth_client_secret ?? ''); ?>" autocomplete="new-password">
+                                <div class="input-group-append"><span class="input-group-text"><i class="fa fa-fw fa-eye"></i></span></div>
+                            </div>
                         </div>
                     </div>
 
                     <div class="form-group" id="tenant_row" style="display:none;">
-                        <label>Tenant ID (Microsoft 365 only)</label>
+                        <label>Tenant ID <small class="text-muted">— Microsoft 365 only</small></label>
                         <div class="input-group">
                             <div class="input-group-prepend"><span class="input-group-text"><i class="fa fa-fw fa-building"></i></span></div>
-                            <input type="text" class="form-control" name="config_mail_oauth_tenant_id"
-                                   value="<?php echo nullable_htmlentities($config_mail_oauth_tenant_id ?? ''); ?>">
+                            <input type="text" class="form-control" name="config_mail_oauth_tenant_id" value="<?php echo nullable_htmlentities($config_mail_oauth_tenant_id ?? ''); ?>">
                         </div>
                     </div>
 
-                    <div class="form-group">
-                        <label>Refresh Token</label>
+                    <div class="form-row">
+                        <div class="form-group col-md-6">
+                            <label>Refresh Token</label>
+                            <textarea class="form-control" name="config_mail_oauth_refresh_token" rows="2" placeholder="Paste refresh token, or use Connect below"><?php echo nullable_htmlentities($config_mail_oauth_refresh_token ?? ''); ?></textarea>
+                        </div>
+                        <div class="form-group col-md-6">
+                            <label>Access Token <small class="text-muted">— optional</small></label>
+                            <textarea class="form-control" name="config_mail_oauth_access_token" rows="2" placeholder="Blank = auto-refresh from the refresh token"><?php echo nullable_htmlentities($config_mail_oauth_access_token ?? ''); ?></textarea>
+                            <small class="form-text text-muted">Expires at: <?php echo !empty($config_mail_oauth_access_token_expires_at) ? htmlspecialchars($config_mail_oauth_access_token_expires_at) : 'n/a'; ?></small>
+                        </div>
+                    </div>
+
+                    <div class="form-group" id="ms_connect_group" style="display:none;">
+                        <label>Microsoft OAuth Connect (Web)</label>
                         <div class="input-group">
-                            <div class="input-group-prepend"><span class="input-group-text"><i class="fa fa-fw fa-sync-alt"></i></span></div>
-                            <textarea class="form-control" name="config_mail_oauth_refresh_token" rows="2"
-                                      placeholder="Paste refresh token"><?php echo nullable_htmlentities($config_mail_oauth_refresh_token ?? ''); ?></textarea>
+                            <div class="input-group-prepend"><span class="input-group-text"><i class="fa fa-fw fa-link"></i></span></div>
+                            <input type="text" class="form-control" readonly value="<?php echo htmlspecialchars($mail_oauth_callback_uri); ?>">
+                            <div class="input-group-append">
+                                <button type="submit" name="oauth_connect_microsoft_mail" class="btn btn-outline-primary">
+                                    <i class="fab fa-fw fa-microsoft mr-2"></i>Connect Microsoft 365
+                                </button>
+                            </div>
                         </div>
+                        <small class="form-text text-muted">Add this callback URI in your Entra App Registration, save credentials, then click Connect to store the refresh token automatically.</small>
                     </div>
 
-                    <div class="form-group">
-                        <label>Access Token (optional – will refresh if expired)</label>
+                    <hr>
+                    <button type="submit" name="edit_mail_oauth_settings" class="btn btn-primary text-bold"><i class="fas fa-check mr-2"></i>Save OAuth Credentials</button>
+                </form>
+            </div>
+
+            <!-- ============================ FROM ADDRESSES ============================ -->
+            <div class="tab-pane fade" id="tab-from" role="tabpanel">
+                <form action="post.php" method="post" autocomplete="off">
+                    <input type="hidden" name="csrf_token" value="<?php echo $_SESSION['csrf_token']; ?>">
+
+                    <p class="text-muted">Each From address must be allowed to send on behalf of the SMTP user.</p>
+
+                    <table class="table table-sm">
+                        <thead>
+                            <tr>
+                                <th style="width:24%">Purpose</th>
+                                <th>From Email</th>
+                                <th>From Name</th>
+                            </tr>
+                        </thead>
+                        <tbody>
+                            <tr>
+                                <td class="align-middle">System Default<br><small class="text-muted">share links, system tasks</small></td>
+                                <td class="align-middle"><input type="email" class="form-control form-control-sm" name="config_mail_from_email" placeholder="noreply@yourcompany.com" value="<?php echo nullable_htmlentities($config_mail_from_email); ?>"></td>
+                                <td class="align-middle"><input type="text" class="form-control form-control-sm" name="config_mail_from_name" placeholder="YourCompany" value="<?php echo nullable_htmlentities($config_mail_from_name); ?>"></td>
+                            </tr>
+                            <tr>
+                                <td class="align-middle">Invoices</td>
+                                <td class="align-middle"><input type="email" class="form-control form-control-sm" name="config_invoice_from_email" placeholder="billing@yourcompany.com" value="<?php echo nullable_htmlentities($config_invoice_from_email); ?>"></td>
+                                <td class="align-middle"><input type="text" class="form-control form-control-sm" name="config_invoice_from_name" placeholder="YourCompany Billing" value="<?php echo nullable_htmlentities($config_invoice_from_name); ?>"></td>
+                            </tr>
+                            <tr>
+                                <td class="align-middle">Quotes</td>
+                                <td class="align-middle"><input type="email" class="form-control form-control-sm" name="config_quote_from_email" placeholder="sales@yourcompany.com" value="<?php echo nullable_htmlentities($config_quote_from_email); ?>"></td>
+                                <td class="align-middle"><input type="text" class="form-control form-control-sm" name="config_quote_from_name" placeholder="YourCompany Sales" value="<?php echo nullable_htmlentities($config_quote_from_name); ?>"></td>
+                            </tr>
+                            <tr>
+                                <td class="align-middle">Tickets</td>
+                                <td class="align-middle"><input type="email" class="form-control form-control-sm" name="config_ticket_from_email" placeholder="support@yourcompany.com" value="<?php echo nullable_htmlentities($config_ticket_from_email); ?>"></td>
+                                <td class="align-middle"><input type="text" class="form-control form-control-sm" name="config_ticket_from_name" placeholder="YourCompany Support" value="<?php echo nullable_htmlentities($config_ticket_from_name); ?>"></td>
+                            </tr>
+                        </tbody>
+                    </table>
+
+                    <button type="submit" name="edit_mail_from_settings" class="btn btn-primary text-bold"><i class="fas fa-check mr-2"></i>Save From Addresses</button>
+                </form>
+            </div>
+
+            <!-- ============================ TESTS ============================ -->
+            <div class="tab-pane fade" id="tab-tests" role="tabpanel">
+
+                <?php if (!$send_ready && !$imap_ready && !$oauth_has_required_fields) { ?>
+                    <div class="alert alert-secondary mb-0">
+                        <i class="fas fa-fw fa-info-circle mr-2"></i>Finish configuring Sending, Receiving, or OAuth (plus at least one From address) to unlock the tests.
+                    </div>
+                <?php } ?>
+
+                <?php if ($send_ready) { ?>
+                <div class="mb-4">
+                    <h6 class="text-bold"><i class="fas fa-fw fa-paper-plane mr-2"></i>Send a Test Email</h6>
+                    <form action="post.php" method="post" autocomplete="off">
+                        <input type="hidden" name="csrf_token" value="<?php echo $_SESSION['csrf_token']; ?>">
                         <div class="input-group">
-                            <div class="input-group-prepend"><span class="input-group-text"><i class="fa fa-fw fa-shield-alt"></i></span></div>
-                            <textarea class="form-control" name="config_mail_oauth_access_token" rows="2"
-                                      placeholder="Can be left blank; system refreshes using the refresh token"><?php echo nullable_htmlentities($config_mail_oauth_access_token ?? ''); ?></textarea>
+                            <select class="form-control select2" name="test_email" required>
+                                <option value="">- Select a From address -</option>
+                                <?php if ($config_mail_from_email) { ?><option value="1"><?php echo nullable_htmlentities($config_mail_from_name); ?> (<?php echo nullable_htmlentities($config_mail_from_email); ?>)</option><?php } ?>
+                                <?php if ($config_invoice_from_email) { ?><option value="2"><?php echo nullable_htmlentities($config_invoice_from_name); ?> (<?php echo nullable_htmlentities($config_invoice_from_email); ?>)</option><?php } ?>
+                                <?php if ($config_quote_from_email) { ?><option value="3"><?php echo nullable_htmlentities($config_quote_from_name); ?> (<?php echo nullable_htmlentities($config_quote_from_email); ?>)</option><?php } ?>
+                                <?php if ($config_ticket_from_email) { ?><option value="4"><?php echo nullable_htmlentities($config_ticket_from_name); ?> (<?php echo nullable_htmlentities($config_ticket_from_email); ?>)</option><?php } ?>
+                            </select>
+                            <input type="email" class="form-control" name="email_to" placeholder="Send to address">
+                            <div class="input-group-append">
+                                <button type="submit" name="test_email_smtp" class="btn btn-success"><i class="fas fa-fw fa-paper-plane mr-2"></i>Send</button>
+                            </div>
                         </div>
-                        <small class="text-secondary">
-                            Expires at: <?php echo !empty($config_mail_oauth_access_token_expires_at) ? htmlspecialchars($config_mail_oauth_access_token_expires_at) : 'n/a'; ?>
-                        </small>
-                    </div>
+                    </form>
                 </div>
+                <?php } ?>
 
-                <?php
-                if (defined('BASE_URL') && !empty(BASE_URL)) {
-                    $mail_oauth_callback_uri = rtrim((string) BASE_URL, '/') . '/admin/oauth_microsoft_mail_callback.php';
-                } else {
-                    $mail_oauth_callback_uri = 'https://' . rtrim((string) $config_base_url, '/') . '/admin/oauth_microsoft_mail_callback.php';
-                }
-                ?>
-
-                <div class="form-group">
-                    <label>Microsoft OAuth Connect (Web)</label>
-                    <div class="input-group">
-                        <div class="input-group-prepend">
-                            <span class="input-group-text"><i class="fa fa-fw fa-link"></i></span>
-                        </div>
-                        <input type="text" class="form-control" readonly value="<?php echo htmlspecialchars($mail_oauth_callback_uri); ?>">
-                        <div class="input-group-append">
-                            <button type="submit" name="oauth_connect_microsoft_mail" class="btn btn-outline-primary">
-                                <i class="fab fa-fw fa-microsoft mr-2"></i>Connect Microsoft 365
-                            </button>
-                        </div>
-                    </div>
-                    <small class="text-secondary">
-                        Add this callback URI in Entra App Registration, then click Connect to authorize and store refresh token automatically.
-                    </small>
+                <?php if ($imap_ready) { ?>
+                <div class="mb-4">
+                    <h6 class="text-bold"><i class="fas fa-fw fa-plug mr-2"></i>Test IMAP Connection</h6>
+                    <form action="post.php" method="post" autocomplete="off">
+                        <input type="hidden" name="csrf_token" value="<?php echo $_SESSION['csrf_token']; ?>">
+                        <button type="submit" name="test_email_imap" class="btn btn-success"><i class="fas fa-fw fa-inbox mr-2"></i>Test IMAP</button>
+                    </form>
                 </div>
+                <?php } ?>
 
-                <hr>
+                <?php if ($oauth_has_required_fields) { ?>
+                <div>
+                    <h6 class="text-bold"><i class="fas fa-fw fa-sync-alt mr-2"></i>Test OAuth Token Refresh</h6>
+                    <form action="post.php" method="post" autocomplete="off">
+                        <input type="hidden" name="csrf_token" value="<?php echo $_SESSION['csrf_token']; ?>">
+                        <input type="hidden" name="oauth_provider" value="<?php echo htmlspecialchars($oauth_provider_for_test); ?>">
+                        <p class="text-muted mb-2">Validates the refresh token and stores a new access token for <?php echo $oauth_provider_for_test === 'microsoft_oauth' ? 'Microsoft 365' : 'Google Workspace'; ?>.</p>
+                        <button type="submit" name="test_oauth_token_refresh" class="btn btn-success"><i class="fas fa-fw fa-sync-alt mr-2"></i>Test OAuth Token Refresh</button>
+                    </form>
+                </div>
+                <?php } ?>
 
-                <button type="submit" name="edit_mail_imap_settings" class="btn btn-primary text-bold"><i class="fas fa-check mr-2"></i>Save</button>
+            </div>
 
-            </form>
         </div>
     </div>
-
-    <div class="card card-dark">
-        <div class="card-header py-3">
-            <h3 class="card-title"><i class="fas fa-fw fa-paper-plane mr-2"></i>Mail From Configuration</h3>
-        </div>
-        <div class="card-body">
-            <form action="post.php" method="post" autocomplete="off">
-                <input type="hidden" name="csrf_token" value="<?php echo $_SESSION['csrf_token'] ?>">
-
-                <p>Each of the "From Email" Addresses need to be able to send email on behalf of the SMTP user configured above
-                <h5>System Default</h5>
-                <p class="text-secondary">(used for system tasks such as sending share links)</p>
-                <div class="form-group">
-                    <label>From Email</label>
-                    <div class="input-group">
-                        <div class="input-group-prepend">
-                            <span class="input-group-text"><i class="fa fa-fw fa-envelope"></i></span>
-                        </div>
-                        <input type="email" class="form-control" name="config_mail_from_email" placeholder="Email Address (ex noreply@yourcompany.com)" value="<?php echo nullable_htmlentities($config_mail_from_email); ?>">
-                    </div>
-                </div>
-
-                <div class="form-group">
-                    <label>From Name</label>
-                    <div class="input-group">
-                        <div class="input-group-prepend">
-                            <span class="input-group-text"><i class="fa fa-fw fa-tag"></i></span>
-                        </div>
-                        <input type="text" class="form-control" name="config_mail_from_name" placeholder="Name (ex YourCompany)" value="<?php echo nullable_htmlentities($config_mail_from_name); ?>">
-                    </div>
-                </div>
-
-                <h5>Invoices</h5>
-                <p class="text-secondary">(used for when invoice emails are sent)</p>
-
-                <div class="form-group">
-                    <label>From Email</label>
-                    <div class="input-group">
-                        <div class="input-group-prepend">
-                            <span class="input-group-text"><i class="fa fa-fw fa-envelope"></i></span>
-                        </div>
-                        <input type="email" class="form-control" name="config_invoice_from_email" placeholder="Email (ex billing@yourcompany.com)" value="<?php echo nullable_htmlentities($config_invoice_from_email); ?>">
-                    </div>
-                </div>
-
-                <div class="form-group">
-                    <label>From Name</label>
-                    <div class="input-group">
-                        <div class="input-group-prepend">
-                            <span class="input-group-text"><i class="fa fa-fw fa-tag"></i></span>
-                        </div>
-                        <input type="text" class="form-control" name="config_invoice_from_name" placeholder="Name (ex CompanyName Billing)" value="<?php echo nullable_htmlentities($config_invoice_from_name); ?>">
-                    </div>
-                </div>
-
-                <h5>Quotes</h5>
-                <p class="text-secondary">(used for when quote emails are sent)</p>
-
-                <div class="form-group">
-                    <label>From Email</label>
-                    <div class="input-group">
-                        <div class="input-group-prepend">
-                            <span class="input-group-text"><i class="fa fa-fw fa-envelope"></i></span>
-                        </div>
-                        <input type="email" class="form-control" name="config_quote_from_email" placeholder="Email (ex sales@yourcompany.com)" value="<?php echo nullable_htmlentities($config_quote_from_email); ?>">
-                    </div>
-                </div>
-
-                <div class="form-group">
-                    <label>From Name</label>
-                    <div class="input-group">
-                        <div class="input-group-prepend">
-                            <span class="input-group-text"><i class="fa fa-fw fa-tag"></i></span>
-                        </div>
-                        <input type="text" class="form-control" name="config_quote_from_name" placeholder="Name (ex YourCompany Sales)" value="<?php echo nullable_htmlentities($config_quote_from_name); ?>">
-                    </div>
-                </div>
-
-                <h5>Tickets</h5>
-                <p class="text-secondary">(used for when tickets are created and emailed to a client)</p>
-
-                <div class="form-group">
-                    <label>From Email</label>
-                    <div class="input-group">
-                        <div class="input-group-prepend">
-                            <span class="input-group-text"><i class="fa fa-fw fa-envelope"></i></span>
-                        </div>
-                        <input type="email" class="form-control" name="config_ticket_from_email" placeholder="Email (ex support@yourcompany.com)" value="<?php echo nullable_htmlentities($config_ticket_from_email); ?>">
-                    </div>
-                </div>
-
-                <div class="form-group">
-                    <label>From Name</label>
-                    <div class="input-group">
-                        <div class="input-group-prepend">
-                            <span class="input-group-text"><i class="fa fa-fw fa-tag"></i></span>
-                        </div>
-                        <input type="text" class="form-control" name="config_ticket_from_name" placeholder="Name (ex YourCompany Support)" value="<?php echo nullable_htmlentities($config_ticket_from_name); ?>">
-                    </div>
-                </div>
-
-                <hr>
-
-                <button type="submit" name="edit_mail_from_settings" class="btn btn-primary text-bold"><i class="fas fa-check mr-2"></i>Save</button>
-
-            </form>
-        </div>
-    </div>
-
-    <?php
-    $smtp_standard_ready = !empty($config_smtp_host)
-        && !empty($config_smtp_port)
-        && !empty($config_mail_from_email)
-        && !empty($config_mail_from_name);
-
-    $smtp_oauth_ready = ($config_smtp_provider === 'google_oauth' || $config_smtp_provider === 'microsoft_oauth')
-        && !empty($config_mail_from_email)
-        && !empty($config_mail_from_name)
-        && !empty($config_mail_oauth_client_id)
-        && !empty($config_mail_oauth_client_secret)
-        && !empty($config_mail_oauth_refresh_token)
-        && ($config_smtp_provider !== 'microsoft_oauth' || !empty($config_mail_oauth_tenant_id));
-    ?>
-
-    <?php if ($smtp_standard_ready || $smtp_oauth_ready) { ?>
-
-    <div class="card card-dark">
-        <div class="card-header py-3">
-            <h3 class="card-title"><i class="fas fa-fw fa-paper-plane mr-2"></i>Test Email Sending</h3>
-        </div>
-        <div class="card-body">
-            <form action="post.php" method="post" autocomplete="off">
-                <input type="hidden" name="csrf_token" value="<?php echo $_SESSION['csrf_token'] ?>">
-
-                <div class="input-group">
-                    <select class="form-control select2" name="test_email" required>
-                        <option value="">- Select an Email Address to send from -</option>
-                        <?php
-                        if ($config_mail_from_email) {
-                        ?>
-                        <option value="1"><?php echo nullable_htmlentities($config_mail_from_name); ?> (<?php echo nullable_htmlentities($config_mail_from_email); ?>)</option>
-                        <?php } ?>
-
-                        <?php
-                        if ($config_invoice_from_email) {
-                        ?>
-                        <option value="2"><?php echo nullable_htmlentities($config_invoice_from_name); ?> (<?php echo nullable_htmlentities($config_invoice_from_email); ?>)</option>
-                        <?php } ?>
-
-                        <?php
-                        if ($config_quote_from_email) {
-                        ?>
-                        <option value="3"><?php echo nullable_htmlentities($config_quote_from_name); ?> (<?php echo nullable_htmlentities($config_quote_from_email); ?>)</option>
-                        <?php } ?>
-
-                        <?php
-                        if ($config_ticket_from_email) {
-                        ?>
-                        <option value="4"><?php echo nullable_htmlentities($config_ticket_from_name); ?> (<?php echo nullable_htmlentities($config_ticket_from_email); ?>)</option>
-                        <?php } ?>
-
-
-                    </select>
-                    <input type="email" class="form-control " name="email_to" placeholder="Email address to send to">
-                    <div class="input-group-append">
-                        <button type="submit" name="test_email_smtp" class="btn btn-success"><i class="fas fa-fw fa-paper-plane mr-2"></i>Send</button>
-                    </div>
-                </div>
-            </form>
-        </div>
-    </div>
-
-    <?php } ?>
-
-    <?php
-    $imap_standard_ready = !empty($config_imap_username)
-        && !empty($config_imap_password)
-        && !empty($config_imap_host)
-        && !empty($config_imap_port);
-
-    $imap_oauth_ready = ($config_imap_provider === 'google_oauth' || $config_imap_provider === 'microsoft_oauth')
-        && !empty($config_imap_username)
-        && !empty($config_mail_oauth_client_id)
-        && !empty($config_mail_oauth_client_secret)
-        && !empty($config_mail_oauth_refresh_token)
-        && ($config_imap_provider !== 'microsoft_oauth' || !empty($config_mail_oauth_tenant_id));
-    ?>
-
-    <?php if ($imap_standard_ready || $imap_oauth_ready) { ?>
-
-    <div class="card card-dark">
-        <div class="card-header py-3">
-            <h3 class="card-title"><i class="fas fa-fw fa-plug mr-2"></i>Test IMAP Connection</h3>
-        </div>
-        <div class="card-body">
-            <form action="post.php" method="post" autocomplete="off">
-                <input type="hidden" name="csrf_token" value="<?php echo $_SESSION['csrf_token'] ?>">
-
-                <div class="input-group-append">
-                    <button type="submit" name="test_email_imap" class="btn btn-success"><i class="fas fa-fw fa-inbox mr-2"></i>Test</button>
-                </div>
-            </form>
-        </div>
-    </div>
-
-    <?php } ?>
-
-    <?php
-    $oauth_provider_for_test = '';
-    if ($config_imap_provider === 'google_oauth' || $config_imap_provider === 'microsoft_oauth') {
-        $oauth_provider_for_test = $config_imap_provider;
-    } elseif ($config_smtp_provider === 'google_oauth' || $config_smtp_provider === 'microsoft_oauth') {
-        $oauth_provider_for_test = $config_smtp_provider;
-    }
-
-    $oauth_has_required_fields = !empty($oauth_provider_for_test)
-        && !empty($config_mail_oauth_client_id)
-        && !empty($config_mail_oauth_client_secret)
-        && !empty($config_mail_oauth_refresh_token)
-        && ($oauth_provider_for_test !== 'microsoft_oauth' || !empty($config_mail_oauth_tenant_id));
-    ?>
-
-    <?php if ($oauth_has_required_fields) { ?>
-
-    <div class="card card-dark">
-        <div class="card-header py-3">
-            <h3 class="card-title"><i class="fas fa-fw fa-key mr-2"></i>Test OAuth Token Refresh</h3>
-        </div>
-        <div class="card-body">
-            <form action="post.php" method="post" autocomplete="off">
-                <input type="hidden" name="csrf_token" value="<?php echo $_SESSION['csrf_token'] ?>">
-                <input type="hidden" name="oauth_provider" value="<?php echo htmlspecialchars($oauth_provider_for_test); ?>">
-
-                <p class="text-secondary mb-3">
-                    This validates your refresh token and stores a new access token for
-                    <?php echo $oauth_provider_for_test === 'microsoft_oauth' ? 'Microsoft 365' : 'Google Workspace'; ?>.
-                </p>
-
-                <button type="submit" name="test_oauth_token_refresh" class="btn btn-success">
-                    <i class="fas fa-fw fa-sync-alt mr-2"></i>Test OAuth Token Refresh
-                </button>
-            </form>
-        </div>
-    </div>
-
-    <?php } ?>
+</div>
 
 <script>
-(function(){
-  function setDisabled(c, d){ if(c) c.querySelectorAll('input,select,textarea').forEach(el => el.disabled = !!d); }
-  function show(el, v){ if(el) el.style.display = v ? '' : 'none'; }
-  function val(s){ return (s && s.value) || ''; }
-  function isStd(v){ return v === 'standard_imap' || v === 'standard_smtp'; }
-  function isOauth(v){ return v === 'google_oauth' || v === 'microsoft_oauth'; }
+(function () {
+    function setDisabled(c, d) { if (c) c.querySelectorAll('input,select,textarea').forEach(el => el.disabled = !!d); }
+    function show(el, v) { if (el) el.style.display = v ? '' : 'none'; }
+    function toggle(el, v) { show(el, v); setDisabled(el, !v); }
+    function val(s) { return (s && s.value) || ''; }
+    function isStd(v) { return v === 'standard_imap' || v === 'standard_smtp'; }
+    function isOauth(v) { return v === 'google_oauth' || v === 'microsoft_oauth'; }
 
-  const imapSel = document.getElementById('config_imap_provider');
-  const smtpSel = document.getElementById('config_smtp_provider');
+    // ---- Self-contained tab controller (no dependency on the BS tab plugin) ----
+    const navLinks = Array.from(document.querySelectorAll('#mailTabs .nav-link'));
+    const panes = ['tab-smtp', 'tab-imap', 'tab-oauth', 'tab-from', 'tab-tests']
+        .map(id => document.getElementById(id)).filter(Boolean);
 
-  const imapStd  = document.getElementById('standard_fields');
-  const imapPwd  = document.getElementById('imap_password_group');
-  const smtpStd  = document.getElementById('smtp_standard_fields');
-  const smtpPwd  = document.getElementById('smtp_password_group');
-  const smtpAcct = document.getElementById('smtp_oauth_account');
+    function activateTab(target) {
+        navLinks.forEach(l => l.classList.toggle('active', l.getAttribute('data-target') === target));
+        panes.forEach(p => {
+            const on = ('#' + p.id) === target;
+            p.classList.toggle('active', on);
+            p.classList.toggle('show', on);
+        });
+    }
+    navLinks.forEach(l => l.addEventListener('click', function (e) {
+        e.preventDefault();
+        activateTab(l.getAttribute('data-target'));
+    }));
 
-  const oauthBlock = document.getElementById('smtp_oauth_fields'); // shared creds (in IMAP form)
-  const tenantRow  = document.getElementById('tenant_row');
+    // ---- Provider-driven field visibility ----
+    const smtpSel = document.getElementById('config_smtp_provider');
+    const imapSel = document.getElementById('config_imap_provider');
 
-  const imapHint  = document.getElementById('imap_provider_hint');
-  const smtpHint  = document.getElementById('smtp_provider_hint');
-  const oauthHint = document.getElementById('oauth_hint');
+    const smtpConn = document.getElementById('smtp_conn_fields');
+    const smtpUser = document.getElementById('smtp_user_group');
+    const smtpPass = document.getElementById('smtp_pass_group');
+    const smtpPtr  = document.getElementById('smtp_oauth_pointer');
+    const smtpHint = document.getElementById('smtp_provider_hint');
+    const smtpUserLb = document.getElementById('smtp_user_label');
+    const smtpUserHt = document.getElementById('smtp_user_hint');
 
-  function render(){
-    const iv = val(imapSel), sv = val(smtpSel);
+    const imapConn = document.getElementById('imap_conn_fields');
+    const imapUser = document.getElementById('imap_user_group');
+    const imapPass = document.getElementById('imap_pass_group');
+    const imapPtr  = document.getElementById('imap_oauth_pointer');
+    const imapHint = document.getElementById('imap_provider_hint');
+    const imapUserLb = document.getElementById('imap_user_label');
+    const imapUserHt = document.getElementById('imap_user_hint');
 
-    show(imapStd, isStd(iv)); setDisabled(imapStd, !isStd(iv));
-    show(imapPwd, isStd(iv)); setDisabled(imapPwd, !isStd(iv));
+    const oauthTabItem = document.getElementById('tabitem-oauth');
+    const tenantRow = document.getElementById('tenant_row');
+    const msConnect = document.getElementById('ms_connect_group');
+    const oauthHint = document.getElementById('oauth_hint');
 
-    show(smtpStd, isStd(sv)); setDisabled(smtpStd, !isStd(sv));
-    show(smtpPwd, isStd(sv)); setDisabled(smtpPwd, !isStd(sv));
+    function render() {
+        const sv = val(smtpSel), iv = val(imapSel);
 
-    show(smtpAcct, isOauth(sv)); setDisabled(smtpAcct, !isOauth(sv));
+        toggle(smtpConn, isStd(sv));
+        toggle(smtpUser, isStd(sv) || isOauth(sv));
+        toggle(smtpPass, isStd(sv));
+        show(smtpPtr, isOauth(sv));
+        if (smtpUserLb) smtpUserLb.textContent = isOauth(sv) ? 'Authenticated User Email (licensed user)' : 'SMTP Username';
+        if (smtpUserHt) smtpUserHt.innerHTML = isOauth(sv)
+            ? 'The licensed user that completed the OAuth flow &mdash; <strong>not</strong> the From / shared-mailbox address. Becomes the <code>user=</code> identity in the XOAUTH2 string.'
+            : 'Leave blank if no authentication is required.';
+        if (smtpHint) smtpHint.textContent = isOauth(sv) ? 'OAuth: set the authenticated user email here; app credentials live in the OAuth tab.'
+            : isStd(sv) ? 'Standard: host, port, encryption, username & password.' : 'Disabled.';
 
-    const anyOauth = isOauth(iv) || isOauth(sv);
-    show(oauthBlock, anyOauth); setDisabled(oauthBlock, !anyOauth);
+        toggle(imapConn, isStd(iv));
+        toggle(imapUser, isStd(iv) || isOauth(iv));
+        toggle(imapPass, isStd(iv));
+        show(imapPtr, isOauth(iv));
+        if (imapUserLb) imapUserLb.textContent = isOauth(iv) ? 'Mailbox Email (monitored inbox)' : 'IMAP Username';
+        if (imapUserHt) imapUserHt.textContent = isOauth(iv)
+            ? 'The mailbox you monitor for tickets (the account the refresh token was issued for).'
+            : 'The mailbox address to monitor for incoming tickets.';
+        if (imapHint) imapHint.textContent = isOauth(iv) ? 'OAuth: set the mailbox here; app credentials live in the OAuth tab.'
+            : isStd(iv) ? 'Standard: host, port, encryption, username & password.' : 'Disabled.';
 
-    const anyMs = iv === 'microsoft_oauth' || sv === 'microsoft_oauth';
-    show(tenantRow, anyMs); setDisabled(tenantRow, !anyMs);
+        const anyOauth = isOauth(sv) || isOauth(iv);
+        const anyMs = sv === 'microsoft_oauth' || iv === 'microsoft_oauth';
 
-    if (imapHint) imapHint.textContent = isOauth(iv)
-      ? 'OAuth: set the shared credentials below; IMAP username is the mailbox you monitor.'
-      : isStd(iv) ? 'Standard: host, port, encryption, username & password.' : 'Disabled.';
-    if (smtpHint) smtpHint.textContent = isOauth(sv)
-      ? 'OAuth: set the shared credentials below and the OAuth account email (licensed user that authorized the connection).'
-      : isStd(sv) ? 'Standard: host, port, encryption, username & password.' : 'Disabled.';
-    if (oauthHint) oauthHint.textContent = anyMs
-      ? 'Microsoft 365: Client ID/Secret/Tenant from Entra ID; refresh token via the Connect button.'
-      : anyOauth ? 'Google Workspace: Client ID/Secret from Google Cloud; refresh token via consent.'
-      : 'Configure OAuth credentials for the selected provider.';
-  }
+        show(oauthTabItem, anyOauth);
+        toggle(tenantRow, anyMs);
+        toggle(msConnect, anyMs);
+        if (oauthHint) oauthHint.innerHTML = anyMs
+            ? '<i class="fas fa-fw fa-info-circle mr-2"></i>Microsoft 365: Client ID / Secret / Tenant from Entra ID; refresh token via the Connect button below.'
+            : anyOauth ? '<i class="fas fa-fw fa-info-circle mr-2"></i>Google Workspace: Client ID / Secret from Google Cloud; refresh token obtained via the consent flow.'
+            : '<i class="fas fa-fw fa-info-circle mr-2"></i>These credentials are shared by any Sending or Receiving provider set to Google / Microsoft OAuth.';
 
-  if (imapSel) imapSel.addEventListener('change', render);
-  if (smtpSel) smtpSel.addEventListener('change', render);
-  render();
+        // If OAuth tab is no longer relevant but is currently open, fall back to Sending.
+        if (!anyOauth) {
+            const oauthLink = document.querySelector('#mailTabs .nav-link[data-target="#tab-oauth"]');
+            if (oauthLink && oauthLink.classList.contains('active')) activateTab('#tab-smtp');
+        }
+    }
+
+    if (smtpSel) smtpSel.addEventListener('change', render);
+    if (imapSel) imapSel.addEventListener('change', render);
+    document.querySelectorAll('.goto-oauth').forEach(b => b.addEventListener('click', () => activateTab('#tab-oauth')));
+    render();
 })();
 </script>
 
-<?php require_once "../includes/footer.php";
+<?php require_once "../includes/footer.php"; ?>
\ No newline at end of file