I had a problem yesterday with KAV workstation 6.0.3.mumble scanning TLS-encrypted IMAP connections from thunderbird email clients. I've solved the problem now, but thought I'd post in case other people have the same problem.

I've been running KAV w/s for a few months now, and up to now I've had no problem with email. I'm using Windows XP SP3 with the thunderbird email client, connecting to a Linux server. The IMAP connection uses TLS to encrypt the traffic. Both the client and the server are set to always use TLS. TLS is started with the STARTTLS command over the normal IMAP port. KAV updates automatically from a central server that runs the admin kit on Windows 2003 server.

For some reason email stopped working yesterday. The client would hang when trying to read an email and finally display a blank page. I found that I had KAV Mail Anti-Virus active on the client workstation, and disabling this cured the problem. There had been no changes to the email client or the imap server, so I guess that the problem was caused by some change in KAV, perhaps a new version of the AV software or a new definitions file.

I had "ignore encrypted traffic" selected, but that did not prevent the problem from occurring.

I thought I had disabled mail anti virus, so checked the policy on the admin server. I found it was disabled, but wasn't locked. After locking it, it was disabled on the clients.

Lesson #1: It appears that settings in the policy don't do much unless you lock them.

I don't need mail antivirus, and anyway it wouldn't help me as KAV wouldn't be able to scan the TLS-encrypted traffic anyway.

Like I said, it's working fine now because I've disabled mail anti-virus in the policy, but just wanted to post in case this bites anyone else.