Is there a way not to get those generated email login “m#######” as a login for user instead of their actual name?
Nope, unless it’s an FTP user with a real account. Allowing mail-only users to log into the POP/IMAP servers using their email address is on DreamHost’s “any day now” list. They’re trying, but haven’t given up on the idea yet.
Well, you can simply create a new user, and give them an E-mail address. That will avoid the M system. It does give them FTP access as well, but it’s just a storage directory it’s not access to your domains or anything.