How to set default email addresses for a group in Address / Book and mail

The problem:

I have members in a group in my contacts all with two email accounts - MMS email and regular email. Every time I send a mail to the group, the default email is the MMS email when I want it to be their regular work email.

The solution:

Apparently it wasn't very intuitive. I thought I could select the email to set it as default via the text menu, and that's not how it's done.

After some Googling, here's the answer. Go to Edit, Edit Distribution List..., and from there you can configure the default emails for the groups.