User Reg: auto register for @something, otherwise approval queue?

I am using WordPress for a college newspaper website. We use the comment feature, yet we require people to be logged in to comment. I can no longer use LDAP to authenticate against the school’s master system, as they don’t really like such an idea.

So… I would like to automatically approve users who register with an @csbsju.edu email address. Ideally, I would like their email address to be their username, and just drop the username field all together. Is this possible? Thanks!