The Simplest Explanation

A mother-in-law arrives home from the shops to find her son-in-law  Pete in a steaming rage and hurriedly packing his suitcase. "What happened Paddy ?" she asks anxiously. "What happened!!  I'll tell you what happened. I sent an email to my wife telling her  I was coming home today from my fishing trip. I get home...  and guess what I found?? Yes, your daughter, my wife Jean, naked with Tim McDurmt in  our marital bed! This is unforgivable, the end of our marriage.  I'm done. I'm leaving forever!" "Come now, calm down, calm down Paddy!" says his mother-in-law. " There is something very odd going on here.  Jean would never do such  a thing! There must be a simple explanation. I'll go speak to her immediately  and find out what happened." Moments later, the mother-in-law comes back with a big smile.  "There now Pete, you see? I told you there must be a simple  explanation! "Well what is it?" Fumed Pete. "She never got your E-mail!"