So... a few thoughts from someone who is 6 years out, fully reconciled, with a wife who had a business "relationship" for 3 years:
I often urge people to try very hard to distance themselves from their personal situation and try to look at their story more objectively. So many times these stories are littered with "My wife wouldn't do that," despite the fact that cheating spouses often do. Please do yourself a huge favor and do not underestimate the type of deceit your wife is capable of.
The reason that I mention that first is because an earlier poster suggested the possibility that your wife's calling him (and him not responding) may simply have been a signal for him to respond in a different method. There are a million ways for people to communicate other than phone these days - apps, FB messages, burner phones. This is why it's so important to recognize that "she wouldn't do THAT" is like burying your head in the sand. Yes she could and it is very possible she did. Please be aware of the chance that she's still in regular contact with him.
As to your question about their having sex after your marriage, I'm sorry to say that it is very likely. Typically, women have sex with men with whom they have developed an emotional bond. As such, it's very unlikely that her emotions simply turned off on their own because of your marriage. The ongoing communication combined with opportunity creates the likely scenario of physical meetings. Maybe it stopped when she stopped working - but that doesn't mean that it ended when you married. The fact that she kept reaching out (even if it isn't ongoing) isn't a good sign for her having stopped a physical affair. Again, try hard to look at the situation objectively - does it sound plausible that she just "turned it off" after she married you?
How do you find out the truth? I'm a firm believer that you will only get truth from her when she's in a very narrow sweet spot - the point between being scared that she's going to lose her marriage but not so scared that she thinks you're going to use it against her by divorcing. A long time poster here often suggests giving your wife a hall pass of sorts - letting her know that she has one chance to come completely clean and, in return, you promise not to make any sudden decisions for, say 60 days. You are, in essence, trying to encourage her to be totally honest without the fear that you're just going to clobber her with the new information. That might be a possibility for you.
Outside of that, I am also a fan of just telling your wife that you're taking her to lunch. Simply drive her to a location that does polygraph testing, park in the lot, turn to her and say, "You have a lie detector test scheduled in 10 minutes. You start telling me the truth, right now, or we go in and I will find out the truth anyway." This gives her a shock, doesn't give her any prep time, and offers her a "back up against the wall" rationale to start talking. Of course, if she refuses you know where she stands. And, regardless of her answers, you still go through with the test.
Lastly, I wanted to offer some perspective. If she has just been reaching out periodically and if the affair really has been over for a few years (both very big "ifs") then you're going to have a long road ahead of you should you decide to work through it. As someone who has been there, done that I can tell you that a marriage can be way better following infidelity. It DOES happen. That being said, it is extremely difficult and the affair, the self doubt, the work involved never ends. The pain of infidelity gets better but it NEVER goes away.
We talk here about a 2-5 year recovery period - to which I declare a complete and total bullshit. Yes, that is how long it can take to start reclaiming yourself and becoming a functional human being. But for anyone to think that everything is better in 2-5 years is simply naive.
You have a giant task before you and I would suggest that you get all your ducks in a row first and really think through your options. Do you believe your wife is REALLY capable of moving forward - of doing the kind of work necessary to heal an enormous hole in your heart? It takes a very special type of woman who can do that and they are few and far between. If you look at her over the dinner table and, somewhere in the back of your head you're thinking, "Well, she's always been pretty selfish" - that's not someone who's a great candidate for true reconciliation.
I hope this has been of help.
[This message edited by LifeisCrazy at 9:23 AM, November 10th (Friday)]