Well if you've tried disabling Norton, you've already eliminated your firewall as the cause of the problem.
Have you tried deleting your email account from Outlook Express and then recreating it? (It's often what's needed to fix the problem).
In Outlook Express, go to Tools > Accounts > Mail. If you've only got one email account, it should already be highlighted. If not, click on the relevant account to highlight it. Click 'Remove' and 'Yes'. Then click 'Close'.
Now create the account again, using the information here:
http://smarttelecom.ie/guide_mail_guide_oe.htm l
If you still can't send and receive email, it suggests that the problem is at Smart Telecom's end. You can test it by setting up an email account with a different service. Follow the instructions in paragraph 3, et seq, of my post here:
http://www.theanswerbank.co.uk/Technology/Inte rnet/Question407429.html
That will create a new email account for you, with a username such as
[email protected]. Try sending mail to yourself using that account with Outlook Express. (When you've got more than one account with Outlook Express, you can choose which one to use by clicking in the 'From' field of your new mail, and selecting from the drop down menu).
If you can send mail via Gawab, but not via Smart Telecom (and you've already deleted and recreated your account details), the problem is at Smart Telecom's end of things, not with your PC.
Chris