Some information here. Everyone would get an email. The general domain is af.mil, but every base had its own subdomain, f'rex, @lackland.af.mil (or, I guess, @cheyenne.af.mil). Newly-issued email these days is simply @us.af.mil, but it's a slow process and the old emails are grandfathered. Usernames are firstname.lastname or sometimes firstname.lastname2,

It might make sense to have daniel.jackson@cheyenne.af.mil, but cameron.mitchell@us.af.mil, I think?

This kind of stuff is too fun to figure out sometimes. :)

(ETA: This is all Air Force--the Marines, etc. have their own email system)