The emails were in his account... it made a whole lot of sense to me to delete them for a multitude of reasons... When he confronted me about it, he said "way to restablish the trust Heather"....then he said "f@@k you" and he hung up on me.

I don't think he's upset that I was in his email account b/c months ago, I very bluntly told him something was bothering me (I never told him what) and I wanted the password to his account. He gave it without a second thought. So he knew I would be entering his account at some point.

You didn't just enter and look around, you deleted stuff. If someone gave you the key to their house so that you could enter, they could be real upset if you took stuff out while you there... even if it was stolen furniture which they didn't have a right to have. They may not have the right to have that stuff, but then, that doesn't stop them from feeling that they've been violated. That's what appears to be happening in your case.

It seems he thinks I took something that belonged to him.....but they weren't his, they were mine. Am I right on that?

Yes, you're right that he violated your email account when he forwarded copies from your account to his. In effect, he's guilty of the same act you're guilty of, that is engaging in some unauthorized act while in the other's email account. He minimizes his actions while magnifying yours, you're doing the same back.

So I think the reason he said "way to reestablish the trust" points to his feeling that his account was compromised by your act.

Maybe he wanted those copies just in case D came up again.

But all in all, two wrongs won't make anything right here. You can both draw your lines and blame the other, you're both right, and you're both wrong, and fight about this forever.

Is it worth it? It isn't making anything better. There's the health of your relationship to consider, your goals, and if you get into principles such as:

stolen property is still stolen

then that's a legal argument that belongs in a court, not a relationship. Winning in court requires having the winning argument. A relationship doesn't work that way.

Resolving this is going to take you to make the first move. What would be another way to resolve this that doesn't require assigning who's at fault?