In directadmin reseller level when I create a user they can access their inbox through squirrelmail. they can send emails but they can't receive any because there isn't any address. for example when I sent an email to my Yahoo mail. sender's address was firstname.lastname@example.org that i can't reply to it. every user has a different domain so email addresses should be based on their domain. e.g. email@example.com, firstname.lastname@example.org
I have centos installed and as you know with directadmin control panel.
How can I create emails like I explained??