Start with the business purpose
Email authentication helps receiving systems distinguish authorised mail from messages pretending to use your domain. It also makes responsibility visible across the services that send on your behalf.
Map every sender
Your primary mailbox provider is only one source. Website forms, finance platforms, marketing tools and support systems may all send mail. An accurate inventory comes before a strict policy.
Treat records as one control set
SPF lists approved sending infrastructure, DKIM adds a verifiable signature and DMARC connects the result to a policy and reporting address. No single record replaces the other two.
Assign an owner
Domain records, sending-service changes and DMARC reports need an administrative owner. Without one, a well-configured baseline drifts as suppliers change.