Email troubleshooting guides
Microsoft 365 setup guides, organized by problem
Browse Microsoft 365 MX, SPF, and DKIM setup guides for custom domains.
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Microsoft 365: DKIM record not verifyingFix Microsoft 365 DKIM by publishing both tenant-specific selector CNAMEs and enabling signing for the accepted domain.
Microsoft 365: MX records not receiving mailRestore Microsoft 365 inbound delivery by checking the accepted domain, recipient objects, public MX route, and any intentional security gateway.
Microsoft 365: SPF record for provider sendingAuthorize Microsoft 365 and every other legitimate sender in the single SPF policy evaluated for the message envelope domain.
Primary sources: Primary technical reference.