There are mailusers with direct forward to a mailbox

id:vmailmgr-forward-mailbox

We can only support full mailaddresses as forwards in the standard mail system. This error indicates, that you have set up internal mail forwards to a mailuser.

You can find a more detailed list of mailusers with the following command:

[isabell@stardust ~]$ listvdomain
info No post
post Yes

All lines with 3 or more columns contain forwards which should be full mailaddresses. If not you should replace those using the uberspace mail commands.

Warning

Warning: We could migrate this setting automatically to the standard mail system, but it might have minor effects to the current behavior of the mailaddress. You could change the configuration yourself using the uberspace mail commands.