[Dovecot] default domain empty

[Leo Unglaub]

Hi friends,
i have a question. I have a running dovecot install on my server and a
lot of virtual domains. It works great. The users are logging in with
user at domain.tld but one old domain must be logged in with only the
username only (without @domain.tld). My problem is that in this case
the mailbox_localtion don't work. For example:
> mail_location = maildir:/var/mail/%d/%n/maildir:INDEX=/var/mail/%d/%n/indizies
The variable %d is not replaced with the domain. The dokumentation
says: domain part in user at domain, empty if user there's no domain
Okay, but is there a way to add a domain to this beause i need the %%d
for mailbox sharing.

Can i override the domain with a value from the user db or is it
possible with a login script or somethink?
Thank you a lot
Greetings from Austria
Leo