There is an issue with Netscape regarding the use of the "@" symbol in the username.

In order to log into your email account with a username with an embedded "@" using Netscape, you have to go into the users profile directory for Netscape and edit the "prefs.js" file. Add the following line:

user_pref("mail.allow_at_sign_in_user_name",true);

That should fix the issue.