"Your server has unexpectedly terminated the connection...."
For the past couple years, we have recommended Symantec's Norton AntiVirus as the best defense against viruses -- that and using any e-mail client besides Microsoft Outlook. However, Norton AntiVirus's "e-mail scanning" option can cause problems downloading some types mail.
First, let me just say that Norton AntiVirus remains the least intrusive and most user-friendly anti-virus program on the market. Symantec, quick to react to new threats, continues to provide timely updates. For these reasons, we continue to recommend Symantec's Norton AntiVirus over competing products.
That said, Norton AntiVirus's e-mail scanning option is reponsible for the dreaded "Your server has unexpectedly terminated the connection…" error messages clients experience all too often. The error appears when you try to check or download your mail.
It surfaces most often with spam, messages that have been corrupted on purpose in an effort to bypass filters. Other common sources are virus infected computers. Often enough, your e-mail client can download these messages if Norton's e-mail scanning option is disabled.
Ironically enough, according to Symantec, you do not need "e-mail scanning" enabled for your system to be protected from virus infected messages. The inbound and outbound scanning options merely provide a second level of defense.
Normally, having several layers of protection against viruses is a good thing. However, in this case, Norton's e-mail scanning may produce an error similar to the following:
Error: "Your server has unexpectedly terminated the connection. Possible causes…. Number 0X800CCC0F"
We have known this for some time as the problem has existed since the Norton AntiVirus 2000 version. Indeed, the problem was much worse in earlier versions of Norton. That is why every copy of Norton AntiVirus installed by one of our technicians has this feature disabled.
If you are experiencing an error similar to the one noted above and you would rather not disable e-mail scanning as documented on Symantec's site, you may still be able to correct the problem without intervention on our part. To do so, log into your e-mail account using our Web mail system and delete the problematic message.
If you're not sure which message may be causing the problem, start by deleting any spam. If you still can't download your mail, delete any messages with one or more attachments. Please note that you should be able to view the message first without downloading the attachment. Finally, try deleting messages one by one until you are able to check your mail without the error.