My ExW used to do the same thing. Go through my e-mails and check my phone. I never strayed once in our 22 year marriage and never gave her a reason to think otherwise. I was very content to be a one woman guy! So I couldn't understand her actions. I thought it ironic that she would be like that and then have an affair herself. However, upon further thinking on this, quite often people will project their feelings onto those closest to them. In other words my ExW and your W thought because they were contemplating an affair, that we might be doing the same.
I on the other hand have never been a suspicious,jealous insecure spouse. I trusted my ExW completely. As a matter of fact, my ExW sharing her body with another man hurt much less than the absolute betrayal of my trust. It took me scant little to get over the physical part of the affair. It is the breach of trust, the lies, the lack of empathy that killed me.
Those that are suspicious without merit are worthy of suspicion.
Me- 47 W- 45 Married 22 years Together 30 years No Kids, 1 dog, 1 Cat 2005 - 2007 W in MLT 1/08 - Crisis hits 3/08 W drops Bomb and leaves in the middle of the night. Admits to PA 4/08 W files for divorce 8/08 Divorce final