I had an employee leave the company yesterday. I would like his incoming emails to forward to someone else so we don't lose customer communication. 

I can deactivate him as a user, but I presume that turns off his email? 

If I deactivate him, I cannot add his email as an "alias" to someone else's email list because "the name is already taken."

If I do not deactivate him, I presume I have to continue to pay a monthly license to get his emails to forward? 

Tying the user to the email address with no chance to edit seems like a poor choice. 

Am I doing this wrong? What if an employee marries and changes their name, but their user name was their old name?