[Dovecot] User login for SMTP but not for IMAP/POP?

[Martin]

Hello everybody,

I have a question, though I'm not sure if it's a matter of dovecot or
postfix. Or if it's even possible to do at all.

If I understand it correctly, SMTP authentification is done via SASL.
When a user wants to login Postfix queries an external user database
(dovecot). Therefore the SMTP-users are identical to the IMAP/POP-users.

I want to achieve the following: I want some user credentials
(username&password) for a user that is able to login via SMTP, but who
doesn't have a mailbox and therefore shouldn't be able to login via
IMAP/POP.

Is this even possible?
How can it be achieved? Or: does this behaviour have a special name,
which I can google for?


Regards,
Martin