While I don't want to get into a huge debate about whether to expose or not...
I will simply say that some people who post here support DB principals and some people don't.
I can tell you that there are bigger issues in this relationship than whether or not your W is having an affair.
I know for centuries, women have been taught to sit back and do nothing because men cheat and that is just how it is. Men, on the other hand, have a possessive caveman mentality that seems to believe that a woman cheating is much worse than anything a man can ever do. (Hence the story the Scarlett Letter).
Please be aware that if you expose, you are going to have to admit that you snooped and violated her privacy and it is going to get ugly. Just the nature of the beast.
"Acceptance doesn't mean resignation. It means understanding that something is what it is and there's got to be a way through it."--Michael J. Fox