The ability to pre-populate the office locations for the bottom of the email would be really handy. So when you come to changing the location, all you have to do is select the correct address from a drop down or tick box.
Having to type out the address for every location is very time consuming (I am sending emails for 8 locations).
It is also easy to forget to update the address. It might be even better if it was editable in the header section alongside the "Subject" and "From Email".