How to Setup SMTP Authentication in Netscape
Open Netscape Mail & Newsgroups
Click on Edit at the top of the window.
Click on Mail & Newsgroup Accounts Settings from the drop down window.
A window similar to the one below should open.

Next, highlight Outgoing Server at the bottom of the list on the left-hand side.
There will be a window similar to the following;

Check the box labeled "Use name and password".
Make sure the that your username is in the User Name field.
Click OK to close this window.
Done!