what more information would you require? Catching them in the act? Even then you would be probably asking for explanation, asking if OM possibly slipped on wet floor and stuck himself into your W.
I was about to say! Seeing a message from OM to W talking about how he can't concentrate because he's thinking about how he just banged her (AT SCHOOL!!!!!!!) seems pretty cut-and-dried to me.
BB, you now know two things about your W:
1) SHE IS A CHEATER 2) SHE IS A LIAR
Some people take offense when I tell them this, they'll start defending their wife. They'll get mad that I said something that they think attacks her character (what character????) But here's the thing, the sooner you realize what you are up against the sooner you will "see the light" and quit playing her game. You want to give her another chance? See number one above. You want an explanation from her? See number two.
Now I am not saying she is beyond redemption, I've seen marriages rebuilt after cheating. But what I am saying is no matter how wonderful and good and loyal your wife USED to be, right NOW she is a lying cheater. You've got to quit trying to reason and negotiate with her like she's still that old wife you knew, she's no longer that person. She might be again some day, but that's way down the road.
Regarding the snooping, talk to a lawyer. As Joe said, a lot of states have adopted "no fault" D and if yours is one then all the evidence of cheating in the world won't make a difference. And if it doesn't then don't snoop anymore because you already know 1 and 2 above, and that's as bad as it gets. All snooping will do is keep verifying 1 and 2, unless there are legal reasons for it which your L will tell you if there are.
