You also have to set _mta-sts.his-domain TXT "v=STSv1; id=[POLICY VERSION ID];" And you have to update that ID every time the policy hosted on the web ser

You also have to set _mta-sts.his-domain TXT "v=STSv1; id=[POLICY VERSION ID];" And you have to update that ID every time the policy hosted on the web server changes.