itflow/agent/modals/client/client_bulk_email.php

<div class="modal" id="bulkSendEmailModal" tabindex="-1">
    <div class="modal-dialog modal-lg">
        <div class="modal-content">
            <div class="modal-header bg-dark">
                <h5 class="modal-title"><i class="fa fa-fw fa-envelope-open mr-2"></i>Bulk Send Email</h5>
                <button type="button" class="close text-white" data-dismiss="modal">
                    <span>&times;</span>
                </button>
            </div>

            <div class="modal-body">

                <label>From Email / <span class="text-secondary">Display Name</span></label>
                <div class="form-row">

                    <div class="form-group col-sm-6">
                        <select type="text" class="form-control select2" name="mail_from">
                            <option value="<?php echo nullable_htmlentities($config_mail_from_email); ?>">
                                <?php echo nullable_htmlentities("$config_mail_from_name - $config_mail_from_email"); ?></option>
                            <option value="<?php echo nullable_htmlentities($config_invoice_from_email); ?>">
                                <?php echo nullable_htmlentities("$config_invoice_from_name - $config_invoice_from_email"); ?></option>
                            <option value="<?php echo nullable_htmlentities($config_quote_from_email); ?>">
                                <?php echo nullable_htmlentities("$config_quote_from_name - $config_quote_from_email"); ?></option>
                            <option value="<?php echo nullable_htmlentities($config_ticket_from_email); ?>">
                                <?php echo nullable_htmlentities("$config_ticket_from_name - $config_ticket_from_email"); ?></option>
                        </select>
                    </div>

                    <div class="form-group col-sm-6">
                        <input type="text" class="form-control" name="mail_from_name" placeholder="From Name" maxlength="255"
                            value="<?php echo nullable_htmlentities($config_mail_from_name); ?>">
                    </div>
                </div>


                <label>Recipients</label>
                <div class="form-row">

                    <div class="col-md-3">
                        <div class="form-group">
                            <div class="custom-control custom-checkbox">
                                <input type="checkbox" class="custom-control-input" id="contactPrimaryCheckbox" name="primary_contacts" value="1">
                                <label class="custom-control-label" for="contactPrimaryCheckbox">Primary Contacts</label>
                            </div>
                        </div>
                    </div>
                    <div class="col-md-3">
                        <div class="form-group">
                            <div class="custom-control custom-checkbox">
                                <input type="checkbox" class="custom-control-input" id="contactImportantCheckbox" name="important_contacts" value="1">
                                <label class="custom-control-label" for="contactImportantCheckbox">Important Contacts</label>
                            </div>
                        </div>
                    </div>
                    <div class="col-md-3">
                        <div class="form-group">
                            <div class="custom-control custom-checkbox">
                                <input type="checkbox" class="custom-control-input" id="contactBillingCheckbox" name="billing_contacts" value="1">
                                <label class="custom-control-label" for="contactBillingCheckbox">Billing Contacts</label>
                            </div>
                        </div>
                    </div>
                    <div class="col-md-3">
                        <div class="form-group">
                            <div class="custom-control custom-checkbox">
                                <input type="checkbox" class="custom-control-input" id="contactTechnicalCheckbox" name="technical_contacts" value="1">
                                <label class="custom-control-label" for="contactTechnicalCheckbox">Technical Contacts</label>
                            </div>
                        </div>
                    </div>

                </div>

                <div class="form-group">
                    <input type="text" class="form-control" name="subject" placeholder="Subject" maxlength="255">
                </div>

                <div class="form-group">
                    <textarea class="form-control tinymce" name="body"
                        placeholder="Type an email in here"></textarea>
                </div>

                <div class="form-group">
                    <div class="input-group">
                        <div class="input-group-prepend">
                            <span class="input-group-text"><i class="fa fa-fw fa-calendar"></i></span>
                        </div>
                        <input type="datetime-local" class="form-control" name="queued_at">
                    </div>
                </div>

            </div>

            <div class="modal-footer">
                <button type="submit" name="bulk_send_client_email" class="btn btn-primary text-bold"><i class="fas fa-paper-plane mr-2"></i>Send</button>
                <button type="button" class="btn btn-light" data-dismiss="modal"><i class="fa fa-times mr-2"></i>Cancel</button>
            </div>
        </div>
    </div>
</div>