Comment by makeitdouble

As for many standards, the question is less what's available/supported and more what's the format actually used irl.

Half the mail I received from that period was in iso-2022 (a JIS variant), most of the rest was latin-1. I have an auto-generated mail from google plus(!) from 2015 in iso-2022-jp, I actually wonder when Google decided it was safe to fully move to utf-8.