Possibly I wasn't clear...
Lots of people with corporate IDs go home and work (lots of Type As out there) or have a blackberry and want to use their coroprate ID as a return address. This wouldn't be possible and IT mgmt isn't going to implement because corporate mgmt would complain :)
Corp email from home or a Blackberry is pretty standard stuff. Even a small business can set up an email server with a web front end.