Auto-select 'from' when composing a new email
There is a feature in Mac Mail that I found extremely useful.
When composing an email, Mac Mail was able to determine which account I was meant to be sending from based on who I am sending to.
Lets say we have 2 email accounts, account 1, 2 and 3
When I email customer 1, I always use account 2.
When I email customer 2 I always use account 1.
Mac Mail learns this pattern and auto swaps to the correct account when I add the recpient to the email.
In my case I use at least 8 different accounts and on many occasions I've sent from the wrong email account.