You mentioned in your previous thread that you were together 2 years. While it is often recommended in AA that people do not engage in NEW romantic relationships the first year, it is also recommended not making abrupt changes the first year either (and breaking up an existing relationship is a major change) yet he dumped you.
It sounds like some kind of quacking to me and trying to crack the door open to reel you back in.
What are you doing for yourself btw? It seems that you are still very eager to engage in with your ex over what was an unhealthy relationship. Are you secretly hoping that he ll be sober, sweep you off your feet and you two will get back together? \
In general, people who have moved on do not get into those kind of deep conversations or agonize about writing closure letters or not. They just get on with their lives.