A commenter pointed out on my original post about Apple Mail and Gmail that you can manage multiple Gmail identities by separating each email address with a comma. Here are the steps:
- If you have already set up your Gmail identities on Gmail, you can go to the next step. You can't use an alternate address for an identity that you have not confirmed with Gmail. If you haven't added the identity in Gmail yet, you can click "Settings" from the links at the top of you Gmail account and then choose the "Accounts" tab. After you've confirmed the identity with Gmail, you can use it with Apple Mail.
- Open Mail preferences and select your Gmail account.
- The entry box that says "Email Address" could really be titled "Email Addresses". Simply enter all your Gmail identities, each separated by a comma, in this box.
- When composing a new message, you'll now have a drop down box for different email addresses.
Just for curiosity's sake, I tried entering an email address that I hadn't confirmed with Gmail. The message is still sent but the sender was simply set back to my main Gmail address.