How to get Mac Mail to show different Gmail addresses in the reply to field?
I use Gmail for Work along with Mac Mail and how I got around this was by opening:


Preferences > Accounts
Then in the Email Address field I put a comma after the address that was there and then added the other address I wanted to be able to reply from. For me I added 4 different ones just by separating with a space and comma like this:


me@gmail.com, me@mtk.org, sales@mtk.org

Now, when I compose an email, there is a a drop down menu that allows me to choose which address I want to send my message from. The only caveat here, is that all of my addresses end in the same business name and it sounds like yours don't. I don't know how your boss has gmail for work set up, but this is easy to change and worth a try! If it doesn't work you can just go back to how the account was setup before, no harm, no foul.