diff --git a/install/lib/installer_base.lib.php b/install/lib/installer_base.lib.php
index b78f8f4db2afe65297f6529ff5e2cd48127d3ce7..894dafeba6474c5daf1b9f18358ecb5f88052484 100644
--- a/install/lib/installer_base.lib.php
+++ b/install/lib/installer_base.lib.php
@@ -930,6 +930,19 @@ class installer_base {
 
 	public function configure_dovecot() {
 		global $conf;
+		
+		$virtual_transport = 'dovecot';
+		
+		// check if virtual_transport must be changed
+		if ($this->is_update) {
+			$tmp = $inst->db->queryOneRecord("SELECT * FROM ".$conf["mysql"]["database"].".server WHERE server_id = ".$conf['server_id']);
+			$ini_array = ini_to_array(stripslashes($tmp['config']));
+			// ini_array needs not to be checked, because already done in update.php -> updateDbAndIni()
+			
+			if(isset($ini_array['mail']['mailbox_virtual_uidgid_maps']) && $ini_array['mail']['mailbox_virtual_uidgid_maps'] == 'y') {
+				$virtual_transport = 'lmtp:unix:private/dovecot-lmtp';
+			}
+		}
 
 		$config_dir = $conf['dovecot']['config_dir'];
 
@@ -954,7 +967,7 @@ class installer_base {
 		// Adding the amavisd commands to the postfix configuration
 		$postconf_commands = array (
 			'dovecot_destination_recipient_limit = 1',
-			'virtual_transport = dovecot',
+			'virtual_transport = '.$virtual_transport,
 			'smtpd_sasl_type = dovecot',
 			'smtpd_sasl_path = private/auth'
 		);