Bugzilla

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/84.0.4147.89 Safari/537.36

Steps to reproduce:

This is with Thunderbird under macOS (10.14.6).  Steps are:

* Compose a mail
* Hit Send
* While the mail is sending, go back to Inbox and click to read a new message and/or delete it and/or skip to next message.

I'm not sure if the exact trigger is to manipulate Inbox in this way while it's in the sending-SMTP stage, or the saving sent mail to IMAP stage.  I suspect the latter.

This problem occurs frequently, and it has been doing it for a long time, over many different versions of Thunderbird.  (I only just got around to reporting it)


Actual results:

Thunderbird locks up: shows spinning beachball, and does not recover.

Activity Monitor says "Thunderbird (not responding)". Sending regular Quit from Activity Monitor does nothing.  Only solution is to select "Force Quit".

I try to train myself to click Send and wait until the send/save completes, before opening any new mail.


Expected results:

I should be able to read mail, while mail completes sending/saving in the background.

Possibly related to bug 1042784.  However that one says "The UI freezes while sending and while copying to sent folder".  In my case, the UI functions correctly as long as I don't go to read a new mail while the sending/saving is taking place.