So I have been using Thunderbird for the last 5 months so that I have my many e-mail's accessible to one LOCATION to check on. This includes 3 yahoo e-mail accounts, 1 gmail account, and 1 ISP e-mail account.

Up until about 2 weeks ago Thunderbird worked flawless, but recently when I launch Thunderbird and check e-mail it works at the beginning. Then if you leave Thunderbird open for a period of time and then create a new e-mail to someone say 2 hours later and then click send,  it appears as though its going to send the e-mail and then you see a message box showing its attempting to communicate with green status BAR. It then times out and states SOMETHING about the password may be incorrect for the e-mail address.

When this happens I save the e-mails that I want to send as drafts, and then close Thunderbird and then launch Thunderbird again at which point any new e-mail I receive upon reconnection with the mail servers and I can click to send my e-mail from the drafts bin, and they send with no problems.

Anyone SEEN this issue before to point out the cause?

One thing I am going to try is to see if I can extend the time before timeout, but I have doubts that this will fix this issue. I have broadband internet and everything happens quickly when downloading and uploading data etc, so a 16k in size e-mail shouldn't time out and then suggest that I may need to reenter my password.

http://support.ecenica.com/email/troubleshooting-email/how-to-fix-connection-to-server-timeout-error-in-thunderbird/TBird times out... Quote

Thunderbird closes its database after five minutes of inactivity

If I could not resolve that, I think I'd switch to Windows Live Mail.

That's just crazy talk...