Most problems with Nortons can be found by searching the knowledge base
http://www.symantec.com/search/
This was for V2002 but would be relevant to 2003
Ensure that your email program is configured to not automatically disconnect
after sending and receiving email
Examine your email program to ensure that it is not set to automatically
disconnect after sending and receiving email. NAV intercepts outgoing email and
scans them before they are sent to your email provider. If your email program is
set to automatically disconnect after sending and receiving email, then NAV
cannot complete the scanning process and will display this error message.
To fix this problem, turn off the option to automatically disconnect after
sending and receiving email from within your email program. Consult your email
program's documentation for instructions on how to do this.
To change the default time out for Outlook or Outlook Express
If the previous section did not fix the problem, and if you have Outlook or
Outlook Express, then try these steps to increase the Server time out period.
1.. Start Outlook or Outlook Express.
2.. Click Tools and Accounts.
3.. Click the Mail Tab.
4.. Select your email account, and then click Properties.
5.. Click Advanced.
6.. Move the slider under Server Timeouts to 2 minutes.
7.. Click Apply, and then OK.
8.. Send any email messages that are left in the in-box.