Assistance with Microsoft O365 Email Deliverability?

Hi NANOG'ers, Reaching out for help - having troubles with email delivery into O365 inboxes. Have done the requisite PTRs, SPF+DKIM work, domain reputation, RBL checks, etc. For some reason, this one is vexxing me. Anyone from Microsoft on the list that could lend a helping hand? Thanks, Tom -- Tom Daly tjd@q7.io