SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail), and DMARC (Domain-based Message Authentication, Reporting & Conformance) are email authentication protocols that help protect your brand from being impersonated in email campaigns:
SPF allows the owner of a domain to specify which mail servers are permitted to send email on behalf of their domain. DKIM adds a digital signature to your emails, which helps receivers verify that the email was indeed sent by your domain and has not been altered in transit. DMARC builds on SPF and DKIM by providing a way for domain owners to publish policies on how recipients should handle emails that fail SPF or DKIM checks.