My STBXAH used to do the same thing. And he still does, from time to time, with a sappy email, full of overblown sentiment. I don't respond anymore. He knows a divorce is imminent. The texts, the emails---it's all about trying to create guilt within us, so they can get us nicely hooked back into taking care of their every need. This , of course,is to the utter detriment of our own happiness and well-being.
A question I used to ask myself: Who's taking care of MY needs? Certainly not him! And that helped me move on, ignore the quacking, and start putting all that time and energy into MYSELF, where the payoff would be much greater and happier.
Quacking is used by the alcoholic to deflect personal responsibility, and create guilt in the codie. He knows damned good and well why he is alone, but does not want to take responsibility for the choices that got him here. The kindest thing you can do, especially for YOURSELF, is to ignore it, and keep on your path. He also has the right to consequences, one of which he no longer gets to be in your life.
Stay strong! Delete, delete, delete!