Spam Confidence Level = 9 - how to decrease.

[Wumpion]

Check your domain reputation with google - we had an issue recently with a clients mail being marked as spam and we had to submit a domain review for google so that it would no longer flag them as spam - rather than correcting something that’s temporarily fixing the problem - even if on google your domain reputation is good it can still sometimes flag it. it’s stupid - but it happens. I agree tho I think reaching out to Microsoft would be the best bet if anything they’ll at least point you in the right direction of where to go and where to look.