When you're emailing to a group from your Contacts program, you can just type in the group name to have Mail autofill all of those addresses for you.
Depending on your Mail settings, you''ll either see this expanded view after you press Return…
…or this:
So how do you figure out which addresses Mail is sending to? Is it using your Mom's work info or her personal address, for example? And how do you change that permanently for the members of a group?
First of all, if you're only seeing the group name as in my screenshot above, you can expand that to see what's going on. If you click on the small arrow that appears when you hover over the name, you'll see the option to expand the group.
As an aside, whether or not the group you're mailing to shows who's in it is controlled within Mail> Preferences> Composing, and it's labeled When sending to a group, show all member addresses.
If you turn that on, groups will be expanded by default when you type them in, so you don't have to do this every time.
Anyhow, after the group is expanded, hover over any person and click on the white arrow that appears to reveal a contextual menu. This'll tell you which address you're sending to if there are multiple choices, and you can switch it if you want to.
That's good to know, but it can be annoying if you almost always want to send to a different address than the one Mail is defaulting to. And what if you've got a group with hundreds of members? Well, you'll control this behavior using Contacts' distribution list feature, and it's simple as can be. Just open the Contacts program and pick Edit> Edit Distribution List.
You'll then get a list of your groups, and if you choose one, you'll see that the members' email addresses are either in black or grey.
The ones that'll be used when you do a group email are selected in black, so go through and click on the addresses you want to use. That's all there is to it! Press OK when you're done, and from then on, Mail will use the new addresses you picked for the group members when you send a message to everyone.
One more thing: If you go to edit your Contacts distribution list and you see physical addresses or phone numbers instead of emails, note that you can click the column there to change what type of distribution list you're editing.
Changing the distribution list for physical addresses is handy, for example, if you're printing out mailing labels for a group and you want to use specific addresses for everyone. Within the printing dialog box, you can choose which addresses to use from a drop-down—and you'll pick the ones from your configured distribution list.
So if you're trying to edit which emails are used when you're mailing to a group instead, just make sure to toggle that header to the proper category. Easy, right? Right! It's rocking my socks, guys.