SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail), and DMARC (Domain-based Message Authentication, Reporting & Conformance) are email authentication protocols that help to verify the legitimacy of your emails:
SPF: Specifies which IP addresses are allowed to send emails on behalf of your domain. DKIM: Adds a digital signature to your emails, allowing the recipient's server to verify that the email was not altered in transit. DMARC: Builds on SPF and DKIM by providing a mechanism for email receivers to report back to the sender about emails that pass or fail authentication checks.