Try recreating you mail profile.
Deleting you mail profile: (this will delete all of your emails that are on your computer)
- Click Start
- Click Control Panel
- Type Mail in search (on the top right). Click Mail.
- Click Show Profiles...
- Select your Comcast mail profile (it might be the only one).
- Click Remove.
Recreate your mail profile: (Please note that this is for Outlook 2007. The directions should be similar. These directions were found on Comcast's Site)
1. In outlook, choose Tools
2. Choose Account Settings
3. Choose the Email tab
4. Click on your Comcast account to highlight it
5. Choose Change
6. Enter Your Name (whatever you want to appear on your messages)
7. Enter E-mail Address (your full Comcast email address)
8. Choose POP3 as the Account Type
9. Incoming mail server is mail.comcast.net
10. Outgoing mail server is smtp.comcast.net
11. Enter User Name (your Comcast user ID, the part before "@comcast.net" in your email address)
12. Enter Password
13. Check "Remember password"
14. Make sure “Logon using Secure Password Authentication (SPA)” is NOT checked
15. Choose More Settings
16. Go to the Outgoing Server tab
17. Check “My outgoing server (SMTP) requires authentication”
18. Choose “Use same settings as my incoming mail server”
19. Go to the Advanced tab
20. Choose SSL encryption for both incoming and outgoing servers
21. Change port number to 995 for incoming, 587 or 465 for outgoing
22. Bump up the Server Timeouts slider to the high end
23. Click OK, Next, Finish
Other troubleshooting tips can be found on Comcast's Forums.