A simple explanation

The mother-in-law arrives home from the mall to find her son-in-law boiling angry and hurriedly packing his suitcase.
"What happened ?" 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 business trip. I get home... and guess what I found ? Yes, your daughter, my wife , with a naked guy in our marital bed! This is unforgiveable, the end of our marriage. I'm done. I'm leaving forever!"
"Calm down, calm down!" says his mother-in-law. "There is something very odd going on here. My daughter 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.
" I told you there must be a simple explanation .....she didn't receive your E-mail!".��