> Not only Outlook comes with such quirk, AFAIK the mail service that > Tencent provides for personal usage does as well. I don't think it's a > good idea to hardcode the problematic providers. > > Not sure whether similar ideas have been proposed earlier: since this > quirk affects only following e-mails but not the coverletter which > doesn't have a In-reply-to field, is it possible to detect the quirk > with the response of sending the coverletter by comparing the desired > Message-ID and the one in response? We could throw a warning and > automatically fixes following mails if the bad case really happens.
