[Dovecot] mkdir imap with user@domain.com

I have a bit a problem. In a virtual domain enviroment i use for login "user@domain.com" and the password.

in the mysql authentication it works beautiful with %d and %u placeholder.

Now when is whould like ad a folder via imap i get an error

imap(user@domain.com): mkdir(/var/mail/domain.com/user@domain.com/.test) failed: No such file or directory

It should be mkdir(/var/mail/domain.com/user/.test)

Is there a way to configure this?

Thanks Regards Karl-Heinz

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