Can receive emails, but can't send emails

[jhinkens]

I'm running Windows Vista Home Premium with Vista Mail. I'm attempting to set up a new email account but continue to get the following error message:
Your server has unexpectedly terminated the connection. Possible causes for this include server problems, network problems, or a long period of inactivity. Subject 'connor test', Account: 'mail.mainlineautobody.com', Server: 'mail.mainlineautobody.com', Protocol: SMTP, Port: 25, Secure(SSL): No, Error Number: 0x800CCC0F
I've reviewed the threads on this forum with similar problems and took serveral steps to resolve it.
1. The PC is new and came with Norton antivirus pre-loaded although not activated. I uninstalled Norton and installed AVG 8.0 antivirus.
2. I got the same "can't send" results with AVG disabled and even after uninstalling the program.
3. I've replicated the incomiing and outgoing server information with another PC here at my house that works fine, although the other PC is running Outlook 2003 via MS Exchange.
4. I configured this new PC (for my kids) with a POP3 account.
I've tried everything I can muster but no luck. Any additional help would be greatly appreciated.
Thank you,
Joe