distuguish between different domains

Hello!

I asked myself wether it is possible to distinguish between different doamins in dovecot so that a user only sees his mailbox when he is connecting with user1@aaa.de specifying the server with mail.aaa.de for example.

So the server does not handout the mailbox for user1@bbb.de when the client connects to mail.aaa.de as user1@bbb.de

I have this problem with roundcube. Dovecot is responisble for two domains. With roundcube I can login as user1@aaa.de altough the client is configured like so: $config['smtp_server'] = 'tls://mail.bbb.de'; and I am landing in the mailbox of user1@aaa.de

Is there a way to striktly differentiate between doamins? Both domains have their own IP-addresses.

Regards

Andreas