In Outlook Express click 'Tools' at the top then down to 'Accounts...'

Hit 'Add -> Mail...'

Make sure that 'POP3' is selected in the drop down menu.
Enter mail.comstar.com.au or mail.comstar.net.au as both your incoming and outgoing mail servers, depending on your e-mail address.

On the next screen, enter your full Comstar e-mail address as your account name, and your password.
Select the 'Remember Password' checkbox if you don't wish to enter your password every time you check your mail.
Hit 'Next', then 'Finish'.

Then go up to 'Tools' -> 'Accounts...',

Select your account and hit the 'Properties' button, then the 'Servers' tab.
Select the 'My server requires authentication' box and hit apply.
You should now be able to send and receive email. Enjoy.