Add mail templates(with subject and addresses and other things)
Add mail templates(with subject and addresses) in mail.app there is Stationery. It useful when you need to send massage to multiple addresses and other option.
Dennis Plöger commented
There's already a suggestion for that here: http://feedback.airmailapp.com/forums/274948-airmail-mac-3-x/suggestions/5351656-support-for-templates-or-stationery