Ok, I didn't need much prompting and just read his email.
Confirmed he has been living with her since freedom day. He is still seeing her, they went out last weekend and at least exchanged emails today.
I know it shouldn't matter because I already knew in my gut that was going on, but seeing the proof just infuriates me. Now I really want to ask him something point blank, catch him in a lie, tell him off and walk away forever.
There will still be an opportunity to do this, if that's what you want to do. Follow Gucci, and play out the string. Part of that string WILL contain a decision point for your boyfriend, and you will have the benefit of "knowing what you know," so it will be very easy to see if he tells you the truth. At THAT time, you can call him on it if you wish, in whatever MANNER you wish. I'd suggest something a lot stronger and calmer, such as "PLEASE STOP IT. We both know you're lying -- again -- right now, and it's incredibly disrespectful. So when you're ready to deal truthfully with me, let me know. I may or may not have moved on at that point, however."