A lot of this is due to newness and perhaps bad IP reputation. You can fix the reputation by requesting your removal from blocklists. The newness should be fixe

A lot of this is due to newness and perhaps bad IP reputation. You can fix the reputation by requesting your removal from blocklists. The newness should be fixed after a few years - have you run it on the same IPs for those 15 years? In my experience after a year or so the problems go away (admittedly this is on a much larger scale than personal email).