Hello. I work for an IT support company and one of our clients are now having this issue too.   Their SPF, DMARC, DKIM is all correctly configured and no other recipients have issues other than TPG recipients.   If they email from Office 365 (their primary email host) they get this error, but if they email from another approved source (also in the SPF record) the email goes through.   It looks like the issue might be limited to TPG receiving emails from MS Office 365 Senders in my case.   Just wondering if you have had any success in resolving the issue? ... View more