I like the idea of marking his emails so that they go straight to junk or spam so that you don't even have to deal with them.
I feel very much like you in that when lies or distortions are thrown my way I have a VERY hard time not defending or arguing to "prove" the truth. It's stupid of me and at the end of the day leaves me 10 x more upset than I was to begin with. Recognizing what you are inclined to or tempted to do is a definite sign that you're moving fwd though, right?
I think it's good that you wrote out a response that you won't be sending to him but that allowed you to get out what you were thinking/feeling... I think that's something that gets recommended a lot in therapy as a way to deal with feelings that are swirling around and I find that when I do this (write but don't send) it helps me let go of the feelings...
Oh and you're right (IMHO)-- I think that most of the time, people who spend lots of energy spouting half truths, distortions and lies, like your ex bf or my H or whomever, are fully aware on some level that they are misrepresenting reality and they hope that you or I or whomever will respond and give credence to the lies/denial etc...
I think that silence is the loudest message you can send. I've certainly been told this same advice plenty and don't always do a good job of applying it, but I'm trying!