A man sent a message to my wife saying: You will always be my wife.

What is the premise? Is it his wishful thinking? Then you can't blame your wife. It's just that she's so nice. You should cherish her. If they are having an affair, you should be prepared, be careful and have a good talk with your wife. Usually the other half will know about the affair. Don't make wild guesses, make sure before making a decision.