I work for the Ontario government. Several years ago, we consolidated several email systems (about 60,000 people) into one: ontario.ca. We use real names (firstname.lastname@example.org). Numbers are added by default by Exchange if an address is taken (email@example.com), but we let people pick whatever they want if they don't like that: middle initial, even the city they work in if the middle initial isn't enough. It doesn't really matter what their email address is, as long as it's appropriate and has their name in it.