Which port are you using for smtp? Do you have SSL on or off?
Need Email Help? Please post the following information in your post. Do you use XfinityConnect? The Full or Lite version? Do you use an email client? Which one? (Eg; Windows Live mail, Outlook, a smartphone etc.) Which browser/version do you use? And- have you cleared your browser cache? Which operating system? XP, Vista, Windows 7, Mac OS X Details of the problem you are having.
What anti-virus program are you using? Is it checking incoming/outgoing mail? If so, you can turn that part off as both incoming and outgoing e-mails going through the Comcast e-mail servers is put through virus scanning by Comcast.
Because I made the changes, as proposed above, I could no longer retrieve mail. So, I had to change Account Settings - Security Settings: Connection Settings = None and Authentication Method = Password Transmitted Insecurely. I'm now back to retrieveing mail, but still can't send. Also had to change server settings to None & Password transmitted Insecurely.
Suspended virus scan on Norton - didn't help
Suspended Firewall on Norton - didn't help
Suspended all Norton pgms - didn't help
Used command prompt to perform telnet - got error "telnet is not recognized as an internal or external command, operble program or batch file".
Yes, port 25 use doesn't require authentiction unless you are outside the Comcast network, like at a hotel or hotspot somewhere. Also, many people are having port 25 blocked by Comcast at the cable modem, so I highly recommend you to switch to 587, STARTTLS, and simple password authentication.
And no, smtp.comcast.net does not respond to ping.