I’m using Thunderbird, and all too frequently it informs me that my message was sent, but that a copy of the message could not be saved in the IMAP sent folder. Repeated tries to save it do not work UNTIL Avast is turned off for 10 minutes, at which point trying again always results in the save succeeding.
Thanks for your feedback…! 
You can try the latest build of avast: http://forum.avast.com/index.php?topic=59223.0
asyn
I have updated to that release. I’ll say that up until two updates ago, I had no trouble getting or sending my IMAP mail. Now, my connection to IMAP times out constantly unless I turn off Avast protection for 10 minutes to send the message. Likewise, I find that often when I try to receive mail manually, I’m told that Thunderbird is checking the server capabilities (the usual first message), and then it stops. If I suspend Avast protection, and click Receive again, it does everything it should.
np here thb3.04 + Gmail/IMAP and Avast 5.0.545
there has been such issues, like with the saving to the draft folder, in early releases of Avast 5, but not anymore for a long time. Don’t know what’s wrong with your config…
okay I read the end of you last post , which I first skipped…if it works with Avast mail shield disabled, it means that you haven’t configured Thunderbird to work with avast : It shouldn’t work at all normally.
So: when it worked, it meant that the mail shield was just ignoring your settings in Thunderbird. It doesn’t always do that, it can block everything too off and on 
give us your thunderbird configuration
Which part do you need? The server settings for one of the configured IMAP accounts (they’re all the same other than the mailbox name) and the outgoing server settings, or something else?