do you think she's reading YOUR e-mails? Can you set it up where she WILL?
Here's what I'm thinking. Send an e-mail to a friend, along the lines of "I honestly don't know what to do, Steve. I've heard from a friend of hers already that she thinks I put a voice-recorder in her car, and I HONESTLY DON'T KNOW WHAT SHE'S TALKING ABOUT! I have it on pretty good authority that her OM put it there (I have a mutual friend who's also a cop), because he -- get this! -- THINKS SHE IS "CHEATING" ON HIM, BY HAVING SEX WITH ME! LOL! I know I know, this is all so crazy. I really don't know what to do. I love her, and I DON'T want a divorce, but this has all gotten so surreal, and I REALLY don't trust this guy. I know he's lying to her, and from what I've heard about him, she should be very, very careful . . . "
etc., etc., etc.
It's basically a play to use a cheating spouse's own usually very high sense of paranoia AGAINST them, and drive a wedge between them. Basically, the concept is that they spend so much time lying to EVERYONE ELSE in their lives, that there's almost always instances where each of them have ALREADY gotten angry with the other for lying to THEM, and now you pile on top of that, via a channel where you know they'll read it, and without looking too obvious.
