[newbie] smtp Users

Hello list.I was wondering, I have my spammer relay controls on so spammers can't of course steal smtp service from me, but rather than allowing a whole domain to use my smtp, is it possible to allow only a certain user on my system to not only download their pop mail, they can already do this,

[newbie] smtp users

Hello list. I was wondering, I have my spammer relay controls on so spammers can't of course steal smtp service from me, but rather than allowing a whole domain to use my smtp, is it possible to allow only a certain user on my system to not only download their pop mail, they can already do this,