The couple of places I worked had so-called policies that stated there was no personal e-mail allowed into or out of the work system. It was never enforced unless someone got carried away and sent an e-mail to an entire department or something like that. I was told the reason they didn't want this was because it clogs up an already busy e-mail server and they don't want it to get bogged down with non-company stuff.
My husband told me of a situation that happened recently where a lady was supposed to reply to a certain person with an e-mail regarding a religious statement and instead of hitting reply to sender she hit "reply to all." The e-mail went to every single person in her address book, which was the entire work system (a hospital with regional satellites), with somewhere between 1500 and 1600 computers. Needless to say, she got in trouble big time for that one!