Mail - When selecting multiple messages the number of envelopes increases from a couple to many depending on the amount selected.
Mail - Mail gives you the option to display the telephone number across your entire screen so it’s easier for you to read and dial it.
Mail - When you receive an shipment email in your Apple Mail, right click on the tracking number to track its location.
Thunderbird - When receiving a message from a mailing list a “reply list” button replaces the “reply all” button.
iOS - Mail inbox automaticly scrolls to the top when you receive a new email, unless you have already scrolled down through more than 3 emails.