Is my ex trying to send me a message of sorts or is this just my imagination?

I went through a similar situation. Except he did not move in with her and he cheated on me 3 wks after we bought our first home. But anyways, I am sure he is miserable and has many regrets. I would only ume that he is trying to tell you something by having that email sent to your email address. I would let it go and ignore him. It's a good thing he showed you who he really was before the relationship went any further. He's an idiot and deserves to live in his own misery.