I am suddenly getting
554 5.7.1 [TPG-S02] [14P3iRWF032355] Message rejected as it appears to be spam. Use SMTP AUTH, PostOffice, or contact the Postmaster Team <firstname.lastname@example.org> when sending out emails from my outlook. My version of outlook is part of the latest office 365 (desktop). I go send emails via TPG post office this seems to be ok. I am receiving emails ok.
I have called tpg and they said they would escalate it but that was early this morning.