https://docs.microsoft.com/en-us/microsoft-365/security/office-365-security/use-dkim-to-validate-outbound-email?view=o365-worldwide

**dkim**

https://protection.office.com/dkimv2

cname: selector1._domainkey -> selector1-##domain-at##._domainkey.##tenant##.onmicrosoft.com
cname: selector2._domainkey -> selector2-##domain-at##._domainkey.##tenant##.onmicrosoft.com

**dmarc**

txt: _dmarc -> v=DMARC1; p=reject