My exabf's last email to me was just nasty. Mean. And full of denial.
This is why I stopped opening emails.
For my own purposes, I went through all the BS he said in his email and addressed it. Said what I felt and what I wanted to say, and typed it up.
He wins! He's got you dancing!
I know there is no point to sending it to him. It's not going to change anything.
Nope. It won't change a thing except to prolong the drama and nastiness.
Anything I say, he probably realizes on some level that it's the truth, but he chooses to keep being in denial.
No, he will not realize on some level it is the truth. Denial is not really a choice for alcoholics and addicts, it's a very fundamental and vibrant part of the disease and disfunction.
If I did send it to him, he'd probably just call the therapist and accuse me of harrassing him, etc. I'm sure it would just make him angry and I need to stick to NC.
It just gets to me that I had to end contact with him being able to spew all of his lies, and I can't even counter them.
Who the hell cares about his lies!? Give him the gift of having the last word. So what? It'll drive him nuts that you don't respond and that's so much better that spewing anger. Taking the high road is good practice for Life.
I know I have to just let this go. It's hard for me tho. I tend to be argumentative and hate letting people get away with lies.
Today you get to choose (respond) differently!! "Behold! I do a new thing!!" 
Any tips on how to handle this, internally?
This visualization has worked like magic for me on numerous occasions: Imagine that you and xbf are walking along a beautiful path in a sunny meadow. Up ahead there is a hilly ridge. You come to a fork in the path and you have chosen to take the one to the right and he is going left. You stand at the fork for a short while, express your love and gratitude for the lessons and love he has shared. You give him a gentle hug, and in your mind you ask HP to bless him. You say goodbye and part ways. You look back and wave once....and then you move ahead, quickly now, with your face turned up to the sun. The gentle breeze is kissing your hair as you move over the ridge to see what awaits on the other side.