Hi Arun, >How do I add a password for the "a...@mx.testdomain.loc" that I would >use in my mail client program, like Thunderbird, to access the >account? Both for sending and receiving?
receiving is clearly out oft scope here, but implies you will be using an IMAP server. In that case, Dovecot can authenticate against flat files and also provide authentication to Postfix. Documentation about that is very rich and easy to find. Cheers, Nik