SPF publishes which systems are allowed to send mail for a domain. DKIM signs outbound messages so receiving providers can verify the message was authorized and was not altered in transit.
What to consider
DMARC combines authentication results with domain alignment and adds policy plus reporting. A gradual deployment allows the business to identify legitimate sending platforms before enforcing stricter rejection policies.
Email authentication cannot guarantee inbox placement, but it provides an important foundation for domain reputation and helps reduce spoofing of the business identity.