I guess it's worth considering, but I don't know how the program would know what's "convenient" for most or all users. In my case, I rarely empty the Trash folders, and when I close the program I usually want to get out of there quickly and wouldn't be happy about waiting for the compact operation to finish, which can take some time since I have several accounts set up. I prefer to set the threshold high enough (currently 60 MB but I might bump it up a bit) that the reminder doesn't pop up too often. If it does while I'm busy, I can either choose "Remind me later" or just move the box out of the way and keep on with my task until I'm ready. It's a non-modal dialog box, meaning it doesn't prevent you from interacting with the main window.

I've already done as you suggested in making the cache 2,000 MB. That's a good idea. As for when to present the pop up, my thoughts were only suggestions. I think the programmers could figure out a best time to do it. Maybe, as soon as mail download is completed before we get to work. It wouldn't deal with later deletes, but they'd just stack up to the next time.

I just don't know where to send this. Any suggestions?

I just don't know where to send this. Any suggestions?

There is a feedback link on Thunderbird help menu. Perhaps use it. but to save you time here it is again connect.mozilla.org

Thank you.