Exchange Administration

We are looking at letting a few of our department help desks take over some Exchange Administration tasks. Can anyone recommend any good third-party apps that would allow for a help desk to create mailboxes, add users to distribution lists, and not much else? Or is there a way to set this up with existing MS permissions?
Also, one of our departments who would like to do this sits behind a firewall. What ports would need to be opened for Exchange administration tasks (if any)?
Thanks-