I contacted the BH immediately after d-day.
I called his house and he answered the phone.
Ironically, he already knew about the LTA but had not contacted me and had not confronted his wife or my FWH.
This was not his wife's first LTA so he was basically done with the marriage and biding his time until he was ready to divorce.
But, even with all of this it was extremely helpful for me to speak with him. He gave me a lot of details about the MOW as well as email evidence.
I was one of those that needed to know everything.
So the information that the BH gave me was helpful.
We spoke on the phone a few times and even met up once in person to exchange hard copies of emails that he had found years earlier.
I ended up reconciling with my FWH but he ended up divorcing the MOW.
He called me one last time a year or so after d-day to give me a heads up that their divorce was final.
That was helpful too because I was vigilant for any kind of contact from the OW ...just in case....
(she never did contact my FWH again)