Why is "hide my email" coming up as default when I am composing or even replying to messages?

Beginning recently, both when I start to compose a new email but also when I reply to an email that has come to my apple address, Mail is defaulting as "hide my email" for the return address. It gives me an option of using my gmail address, but it does not give me the option of using my .me (or .mac) address. How do I fix what seems to be a new default?

If I x out of the email I am trying to compose twice, Mail will then show my .me account as the sender.