[Evolution] send in background

[Gary Curtin <gary curtin gmx ie>]

Having been a Thunderbird user for many years, in that application I had set message sending to be in background. I am so used to starting a new message after clicking send, that the delay while the message is sent is causing me some frustration. I since selected to send messages through Outbox folder, which reduced the time significantly, but there is still some small delay before the compose window is closed.

Any idea how to improve on this with Evolution3.28.1-2 on Ubuntu 18.04?