I dare say.
I own example. I fire George for a long list of foul deeds. He goes to work for another company and writes email from george@example.com that injures my reputation.
I suspect we are only talking about email addresses provided as part of a commercial service, not as an aspect of one's job. For example, if I have a Nextel cellphone, and then they get bought by Sprint and I decide they now suck, and I move my phone service to T-Mobile so I can get a cool new G1, then Sprint is obliged to release my phone number and let T-Mobile provide my new service using it. However, if I work for Bob's Widgets, and they fire me because I'm a slacker, I'm not expecting I get to keep the number associated with my work-issued cellphone, no matter what carrier issued it... Even if Bob's Widgets was really a carrier providing a phone on their own network... -dorn