SPF, DKIM, and DMARC are three DNS records that work together to prove your email is really from you. Get them right and your messages land in the inbox; get them wrong and they land in spam, or scammers spoof your domain.
SPF (Sender Policy Framework)
A list of the servers allowed to send email for your domain. Receiving servers check it to confirm the sender is authorised.
DKIM (DomainKeys Identified Mail)
A cryptographic signature added to each message, proving it wasn't tampered with in transit and genuinely came from your domain.
DMARC
The policy that tells receivers what to do when SPF or DKIM fails, and sends you reports so you can spot abuse.
The Bottom Line
All three should be configured and set to enforce. Once they are, deliverability improves and your domain is far harder to impersonate.
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