Is it illegal for an employer to send a last paycheck in the mail?

It is not illegal to send a final paycheck in the mail. That being said, you should ensure that you have received the proper amount of severance. I would strongly encourage you to visit the severance pay calculator our firm has developed to see what you are owed (www.SeverancePayCalculator.com). I would also encourage you to call us and have one of our employment lawyers review the circumstances surrounding your termination.