diff --git a/program/lib/Roundcube/rcube_smtp.php b/program/lib/Roundcube/rcube_smtp.php
index b0c61a782..7fb083d4d 100644
--- a/program/lib/Roundcube/rcube_smtp.php
+++ b/program/lib/Roundcube/rcube_smtp.php
@@ -102,8 +102,7 @@ class rcube_smtp
             $helo_host = $CONFIG['smtp_helo_host'];
         }
         else if (!empty($_SERVER['SERVER_NAME'])) {
-            $server_name = rcube_utils::server_name();
-            $helo_host = preg_replace('/:\d+$/', '', $server_name);
+            $helo_host = rcube_utils::server_name();
         }
         else {
             $helo_host = 'localhost';
diff --git a/program/lib/Roundcube/rcube_utils.php b/program/lib/Roundcube/rcube_utils.php
index a00495ae6..79ecbbf4d 100644
--- a/program/lib/Roundcube/rcube_utils.php
+++ b/program/lib/Roundcube/rcube_utils.php
@@ -581,11 +581,11 @@ class rcube_utils
         }
 
         // %n - host
-        $n = preg_replace('/:\d+$/', '', $_SERVER['SERVER_NAME']);
+        $n = self::server_name();
         // %t - host name without first part, e.g. %n=mail.domain.tld, %t=domain.tld
         $t = preg_replace('/^[^\.]+\./', '', $n);
         // %d - domain name without first part
-        $d = preg_replace('/^[^\.]+\./', '', $_SERVER['HTTP_HOST']);
+        $d = preg_replace('/^[^\.]+\./', '', self::server_name($_SERVER['HTTP_HOST']));
         // %h - IMAP host
         $h = $_SESSION['storage_host'] ?: $host;
         // %z - IMAP domain without first part, e.g. %h=imap.domain.tld, %z=domain.tld
@@ -605,23 +605,33 @@ class rcube_utils
     }
 
     /**
-     * Returns the server name after checking it against trusted hostname patterns,
-     * otherwise returns localhost
+     * Returns the given host name after checking it against trusted hostname
+     * patterns, otherwise returns localhost
+     *
+     * @param string $name Hostname to check; use SERVER_NAME if none is given.
+     * @param boolean $strip_port Strip PORT from the host name; default is true.
      *
      * @return string Server name
      */
-    public static function server_name()
+    public static function server_name($name = null, $strip_port = true)
     {
-        $server_name = $_SERVER['SERVER_NAME'];
+        if (!is_string($name)) {
+            $name = $_SERVER['SERVER_NAME'];
+        }
+
+        if ($strip_port) {
+            $name = preg_replace('/:\d+$/', '', $name);
+        }
+
         $trusted_host_patterns = rcube::get_instance()->config->get('trusted_host_patterns', array());
 
-        if (empty($trusted_host_patterns) || in_array($server_name, $trusted_host_patterns)) {
-            return $server_name;
+        if (empty($trusted_host_patterns) || in_array($name, $trusted_host_patterns)) {
+            return $name;
         }
 
         foreach ($trusted_host_patterns as $pattern) {
-            if (preg_match("/$pattern/", $server_name)) {
-                return $server_name;
+            if (preg_match("/$pattern/", $name)) {
+                return $name;
             }
         }