MX + SPF + DKIM + DMARC
DMARC on its own is great for rejecting fraud and spam claiming to be from a disused or oarked domain.
MaX Saxe Design migrated to Microsoft 365 from Google Workspace in June 2021.
We enabled DMARC in August/September 2021.
We should have deployed DMARC along with DKIM at the same time as creating our MX, SPF, autodiscover records.
Microsoft 365 should have prompts for MX, SPF, autodiscover DKIM and DMARC issued at the same time within the first-time configurator - this may need to be an opion or a dropdown like with Lynx and SIPS for Skype.
Every company and small business should use DMARC.
Every ISP should use DMARC for their hosted customer email accounts.