[Dominic]

your move is to demand she stop contacting this strange man. Period. If she doesn't, your marriage is over.

Harsh? Yes. An ultimatum, Yes.

But what your wife is doing is unacceptable. Certainly as unacceptable as if you were contacting a strange female online. While her motives may be strictly innocent (doubtful but possible) - his motives are certainly not.

Granted, your wife may not be getting what she needs from you emotionally - if that's the case, she needs to tell you so and you can discuss and solves things as a couple.

Seriously - this is not behaviour a married man or woman should be doing. At all.

And I know I'm going to get slammed for my harsh line here, but I believe in nipping problems like this in the bud, before they evolve into bigger problems.