Setting Up DKIM/DMARC Office 365

Yahoo is now blocking random M365 Domains that do not have DKIM/DMARC setup.

Step 1 ; Setup DKIM

https://learn.microsoft.com/en-us/microsoft-365/security/office-365-security/email-authentication-dkim-configure?view=o365-worldwide

To sum up: Navigate to the DKIM page and enable DKIM for your domain. The process will fail since CNAME records are not in your DNS. The error will contain the necessary CNAME records. Add these two CNAME Records to your DNS. Once DNS propagates, you can enable that setting. 

Step Two: Setup DMARC

https://learn.microsoft.com/en-us/microsoft-365/security/office-365-security/email-authentication-dmarc-configure?view=o365-worldwide

To Sum Up: 

Add this TXT Record to your DNS (edit the values as described in the above article):

_dmarc.domain  TTL  IN  TXT  "v=DMARC1; p=policy; pct=100"