authentication?

[jim]

I have multiple domains setup with Postfix and I have different users in each domain for now.

I am using RoundCube for Webmail and have "mail.mydomain.com" listed as the default, and only, host.

Now if I enter a user in a different domain, "mail.wrongdomain.com", that user can login and see their email.

Ideally, I'd like to see "username does not exist"....or some other such response which is what I expected..

I was told this is an authentication issue and was wondering the best was to do it with RoundCube. I am using Postfix.

Suggestions?

Thanks,
Jim