The file conflicts with an already existing mail user

id:qmail-username-and-vmailmgr-user-blocking

This error indicates, that you have a qmail file like .qmail-mailbox but likewise a mail user mailbox. The qmail file contains the username and forwards all mails to username@uber.space while the mailuser cannot receive the incoming mails.

You need to fix these conflicting configurations, however the qmail file should be removed to use the standard mail system only.

Error

Error: This configuration is probably not working as expected in the standard mail system. This is why you should recreate this mailaddress yourself using the uberspace mail commands.