I was working to maintain an SBS2003 when I found this error in the EventLog of the server (see the picture).
The error description:
For Microsoft, an "Operation completed successfully" is an error :-?
The error description:
An error occurred during a POP3 transaction to server <pop3 .*****.com [*****/*****.com]>. The error is 0 (the operation completed successfully).
For Microsoft, an "Operation completed successfully" is an error :-?
20 Jan 2006 20:12:07
Generally, about two or three error messages down in the application event log, you will see the true cause of that error. In my case, it was a bad password in the POP3 connector for that account.