Gave it a shot:
Hi *wife*, How are you?
We don't know eachother, my name is Revoh and I'm from *GAF*
I would like to talk to you about a topic concerning your husband and my girlfriend.
When you can, please respond.
Look, I put myself in your position and the truth is that I wouldn't NOT want to know what's going on. It's not fair to either of us.
I'll tell you that your husband *guy* has a sentimental relationship with my girlfriend (now ex) from *my country*.
They talk through Skype, FB, Whatsapp, everyday during office hours and outside all the same. They have been at it for months. They send eachother photos, videos, voice messages. Completely (?). If you are able to get him to show you the logs, you'll see that I'm not lying- that is if your husband has not erased the logs from his PC/cell. But don't worry, I have the logs, and I will send them to you. From what you will read, nothing has happened physically, but that's just because *the guy* couldn't come about a few weeks ago to the country. *Wife's brother* came. In the logs you'll read it is clear that the two of them intend to have sex. As soon as you respond, I will give you the link with a folder with last week's logs.