diff --git a/data/web/inc/vars.inc.php b/data/web/inc/vars.inc.php
index 5164333a..14ead835 100644
--- a/data/web/inc/vars.inc.php
+++ b/data/web/inc/vars.inc.php
@@ -143,5 +143,6 @@ $MAILBOX_DEFAULT_ATTRIBUTES['force_pw_update'] = false;
 // Force password change on next login (only allows login to mailcow UI)
 $MAILBOX_DEFAULT_ATTRIBUTES['sogo_access'] = true;
 
-// Default mailbox format, should not be changed, keep the trailing ":"
-$MAILBOX_DEFAULT_ATTRIBUTES['mailbox_format'] = 'mdbox:';
+// Default mailbox format, should not be changed unless you know exactly, what you do, keep the trailing ":"
+// Check dovecot.conf for further changes (e.g. shared namespace)
+$MAILBOX_DEFAULT_ATTRIBUTES['mailbox_format'] = 'maildir:';