Apple Mail: Manage Recipients with the “Mark Addresses” Feature

Mail’s “Mark addresses not ending with” feature is really handy to know about. Let’s say that you work for a business where you’re constantly exchanging confidential e-mails with your co-workers. Sending those pictures of the office Christmas party to someone outside the company could be pretty disastrous, right? Here’s what you can do to have Mail notify you whenever you’re composing an e-mail to a recipient other than the places or people you specify.

First, choose the Mail > Preferences menu item, and then click on the Composing tab. 

Toggle on Mark addresses not ending with, and then type in the domain of your company (the ending part of the e-mail address, such as,, or 

If you’d like to add more than one, just type the domains in the box with a comma between them. 

From then on, whenever you compose a new message (or reply or forward, as well), any addresses that aren’t within the domain you specified will be called out in red. It’ll also show the outgoing address you’re using in red if it doesn’t match the domain—which can be useful to avoid sending messages from the wrong account, too.

If you’d prefer, you can type entire e-mail addresses into that box instead of just using the domain. 

This’ll mean that any e-mails you send to anyone other than those people will get marked. If you share a lot of off-color jokes with your friends, for example, that’ll be a good way to prevent one getting forwarded to your grandma.

This feature gives you a very quick way to tell if you’ve chosen the correct person and address to send your private information to. So those photos of you passed out underneath your boss’s desk? Those’ll be safe from prying eyes. At least until they’re posted on the company Facebook page.