How to send mail to mailbox with disabled domain?

[Kai Schaetzl]

Thanks for all the replies. I didn't have time to reply earlier.
I went with my first proposed solution. Everything else is simply too much 
hazzle. You would have to set this for every single exception/address/user 
and so on and you cannot be sure that it doesn't bite you some time later 
with a tiny problem you didn't imagine at that time. For instance with 
domain affiliation of users.

Yes, this is a Postfix problem. I just thought first it belongs more to 
Dovecot because it is Dovecot's lmtp that does the final mailbox delivery. 
I changed the SQL code a few times and tried to convince Postfix to 
deliver to virtual users without a domain, but it didn't work. As soon as 
I remove the domain or have an account name like user at whatever Postfix 
uses user@$myorigin (even completely removing the whatever stub) and this 
might have created a problem differentiating users (for instance for 
domain quota). It only delivers to mailboxes without a domain that are 
transport "local". And I wanted to keep that domain "local", anyway.

I setup a stub dummy zone of "mail.localdomain" in Unbound which works as 
a wildcard and setup a fitting domain for that client. This works just 
like a normal domain. I can now reuse this wildcard for any more I might 
need it for.

Kai