I consistently get this error from a ROadrunner account on the Time Warner network:

24/05/2010 02:56:00 POP: username@rochester.rr.com (5) - 3 forwarding (from Viking_River_Cruises@emails.vikingrivercruises.com)
24/05/2010 02:56:00 70x70x66x53x57x48x66x69x54x67x55x56x70x49x49x57x67x48x54x55x69x56x56x57x66x69x67x54x51x65x49x65x13x10.eml already exists in message store
24/05/2010 02:56:01 Socket error: 10061 (Connection is forcefully rejected)

The socket error looks like it is referring to the SMTP connection - the log shows that the email is downloaded, but when the connection is attempted to the SMTP server, that is what is forcefully rejected.

Please check SMTP server settings.