I'm having problems where messages occasionally get scrambled. The account uses an SMTP server on gmail.com . Only the Inbox folder and the All Mail folder get messages scrambled; this doesn't happen to other folders. It seems to happen only if Thunderbird is doing a compression of multiple folders, and another message arrives during the compression. I often get at least 300 messages a day, so this happens a few times a month. Most of them use HTML or something else other than plain text. Messages in the Important folder are not affected, so some of the messages can be recovered from that folder. Enough of the message headers to identify the messages in the list of Inbox nessages is not affected; the scrambling only appears if you try to display the body of the messages. Which messages are affected does not relate well to the order of messages in the Inbox list. I suspect it relates to the order of compression instead. Shutting down Thunderbird and restarting it stops any more incoming messages from being affected, at least as long as they do not arrive during a compression. If Thunderbird controls which messages are downloaded, shutting down any downloads during compressions should be a fix. If the server controls which messages are downloaded, a temporary queue for messages downloaded during compressions may be needed. Unclear of the problem is related to my method of putting a small weight on the Shift key so I can select a series of messages using only one hand (my other hand won't press only the Shift key very well). The problem appeared in a few versions of Thunderbird before I started using the weight.