Avoid delayed message send when editing the Outbox message
I'm always using the feature "Send messages through Outbox folder after 5 minutes" in order to "revoke" or "re-edit" "already sent" mails.
One issue with that: While opening a mail from outbox (pending) end editing, this one could be sent in the meanwhile if editing takes longer. Better solution would be to remove it from Outbox at once and treat it just like a new mail.