Add "send and close" option to "messages in outbox" prompt

I often close eM Client when I have messages in the outbox that I forgot to send, and then I get the pop-up asking if I really want to close or not.

Please consider adding a third option: “send messages and close”.

This is now implemented in 9.0.506

If you want to try the new beta, first make a backup using Menu > Backup, then download it from the Release History.