This is intended to be informational.

When setting up Thunderbird to pull email from a SpamCop filtered email account, be sure to use your full spamcop user id: USERNAME[at]spamcop,net in the IMAP server setup. Simply using the name portion USERNAME will occasionally work, but often fail. This is very confusing. Mail may pull one time, then fail for the next half dozen or so, leaving you searching for connection failures, or timeouts, or race conditions.

Simply setting the User Name correctly in the Server Settings dialog will solve this condition.

I believe this will work the same way for POP, as I was having similar symptoms, before I switched to IMAP in an attempt to repair.

That is the same for EVERY type of connection to the email system. The webmail system contains several domains (spamcop.net, cesmail.net, and I believe others). The entire login name is required (and stated as so everywhere I have seen) to differentiate between accounts. This includes webmail, IMAP, POP, SMTP, as well as the reporting page logins.

The "Official" FAQ for the email service is located at: http://www.spamcop.net/fom-serve/cache/289.html

Please explain where you saw any reference to using only the first part of the username. I would be surprised if it EVER worked.

Oh, it was a simple mistake. I put in just the name by mistake. What was odd was that it worked some of the time. (which is what slowed me down in realizing the problem)

If it had NEVER worked, I would not have started this topic. The fact that it occasionally did work is what may confuse others and I hope this topic will save them some time