Mail Server problem

I installed Argosoft mail server pro on windows 2003 system and I created the mx records.
I have two problems;

1) When I'm using outlook or other web based mail systems to access my pop3 mail account; in the login don't accept short name.for example I created a domain ddesignweb.net and in this domain I created a user "engin". Username is "engin" and pass is "...". But when I'm login don't accept engin;accepts engin@ddesignweb.net for username.Are there any stettings about it?
2) I can login my account in outlook.But I can't send and receive messages in internet. (Bu I can send and receive messages locally)