[Dovecot] LMTP returncode 450?

[Peter Mogensen]

Hi,

How do I get the LMTP-server to know which mailbox's are locally hosted 
and return SMTP code 450 if delivery is attempted to a non local user?

I can see that a lookup in the userdb is done, but now matter what I 
return (1/111) from my checkpassword script I just get:

451 4.3.0 <lp at domain.tld> Internal error occurred. Refer to server log 
for more information.

/Peter