Deleting Users (Ex-employees)

If your users are in a Active Directory and you delete the user there, you will be asked if you want to delete the mailbox as well.

first off before deleting the user you'll want to backup the users emails in the event that you will need the users emails at some point, if using outlook just back the emails up to a pst file then toss it on a tape or a folder on your network. then once you delete the user from active directory it will ask if you want to remove the mailbox as well. if you say yes the users mailbox will be deleted as well. this will remove the email from any groups and distribution lists that exists in the AD.

Another way to do it, I know some companies do it this way, is to change the PW and disable the account. Then if these people are re-hired, even years from now, their accounts can be re-added easily.

Answer 3 is the way we do it now. The problem, one, it leaves an ever increasing distribution list and, two, Exchange generates an error when it tries to post a message to an inactive user. Plus, the company doesn't want any "dead wood."

We always backup a users mailbox then delete the account, this will auto remove them from lists etc.
We do disable accounts for a few months and then delete them later when that user has been confirmed to be gone. We never leave them for 'years' as that is a security risk and can make ad more unmanagable if a lot collect up.