diff --git a/lib/os/class.ISPConfigDebianOS.inc.php b/lib/os/class.ISPConfigDebianOS.inc.php
index 3e9542ba00ffb32594929804573a43a4d4925868..ccaa6e97b3eb3119c4727f20b43ae37903c99b92 100644
--- a/lib/os/class.ISPConfigDebianOS.inc.php
+++ b/lib/os/class.ISPConfigDebianOS.inc.php
@@ -1107,6 +1107,7 @@ mailman-unsubscribe:  "|/var/lib/mailman/mail/mailman unsubscribe mailman"';
 			$replacements = array(
 				'/^\s*\$config\s*\[["\']default_host["\']\]\s*=.*$/m' => '$config[\'default_host\'] = \'localhost\';',
 				'/^\s*\$config\s*\[["\']smtp_server["\']\]\s*=.*$/m' => '$config[\'smtp_server\'] = \'%h\';',
+				'/^\s*\$config\s*\[["\']smtp_port["\']\]\s*=.*$/m' => '$config[\'smtp_port\'] = 25;',
 				'/^\s*\$config\s*\[["\']smtp_user["\']\]\s*=.*$/m' => '$config[\'smtp_user\'] = \'%u\';',
 				'/^\s*\$config\s*\[["\']smtp_pass["\']\]\s*=.*$/m' => '$config[\'smtp_pass\'] = \'%p\';'
 			);