> Um... I don't know how Plesk works (I've heard questionable things about > it's Licensing status, plus it being closed source - I like to be able to > fix my server bugs :)), but unless you are using a different IP address > and POP3/IMAP server instance for each domain, I don't see how you could > be doing this right now.
I have multiple domains in the same IP. I tested Plesk with the same username in 3 different domains. I think the way it works is by comparing username and password and associate it with a domain... Not an elegant solution. When I try to change the password to one that exists on the same username for another domain it give me an error. If it is like this I think I'm going to inform my users to add domain to every login.