Added mail helper

app/Helper/MailHelper.php

@@ -0,0 +1,48 @@
+<?php
+
+namespace Kanboard\Helper;
+
+use Kanboard\Core\Base;
+
+/**
+ * Class MailHelper
+ *
+ * @package Kanboard\Helper
+ * @author  Frederic Guillot
+ */
+class MailHelper extends Base
+{
+    /**
+     * Get the mailbox hash from an email address
+     *
+     * @access public
+     * @param  string  $email
+     * @return string
+     */
+    public function getMailboxHash($email)
+    {
+        if (! strpos($email, '@') || ! strpos($email, '+')) {
+            return '';
+        }
+
+        list($localPart, ) = explode('@', $email);
+        list(, $identifier) = explode('+', $localPart);
+
+        return $identifier;
+    }
+
+    /**
+     * Filter mail subject
+     *
+     * @access public
+     * @param  string $subject
+     * @return string
+     */
+    public function filterSubject($subject)
+    {
+        $subject = str_replace('RE: ', '', $subject);
+        $subject = str_replace('FW: ', '', $subject);
+
+        return $subject;
+    }
+}