diff --git a/CHANGELOG.TXT b/CHANGELOG.TXT
index 1c7820ab..b5e10cba 100644
--- a/CHANGELOG.TXT
+++ b/CHANGELOG.TXT
@@ -12,6 +12,8 @@
 Changes since the 3.0.1 release
 -------------------------------------------------
 
+  - AliasHandler: restrict mailbox subquery to allowed domains to improve
+    performance (except for superadmins ;-) on setups with lots of mailboxes
   - allow switching between dovecot:* password schemes while still accepting
     passwords hashed using the previous dovecot:* scheme
   - FetchmailHandler: use a valid date as default for 'date'
diff --git a/model/AliasHandler.php b/model/AliasHandler.php
index 23e08234..b6b0e4c8 100644
--- a/model/AliasHandler.php
+++ b/model/AliasHandler.php
@@ -48,6 +48,7 @@ class AliasHandler extends PFAHandler {
                     ' SELECT 1 as __is_mailbox, username as __mailbox_username ' .
                     ' FROM ' . table_by_key('mailbox') .
                     ' WHERE username IS NOT NULL ' .
+                    ' AND ' . db_in_clause($this->domain_field, $this->allowed_domains) .
                     ' ) AS __mailbox ON __mailbox_username = address' ),
             'goto_mailbox'  => pacol(   $mbgoto,    $mbgoto,$mbgoto,'bool', 'pEdit_alias_forward_and_store' , ''                                , 0,
                 /*options*/ '',