To help combat spam and email spoofing, industry standards such as SPF, DKIM and DMARC have been developed to verify the sources of incoming and outgoing email. These email authentication protocols help mail servers confirm that messages are coming from legitimate sources and protect your domain from being misused by malicious actors.
Sender Policy Framework (SPF)
SPF is an authentication method that prevents unauthorized servers from sending emails claiming to be from your domain. It works by defining which mail servers are allowed to send messages on behalf of your domain via DNS records.
Proper SPF configuration helps:
- Ensure your legitimate messages are not marked as spam
- Block spoofed emails claiming to have come from your domain
DomainKeys Identified Mail (DKIM)
DKIM adds a digital signature to all outgoing emails. Receiving mail servers use this signature, which are implemented via public-key cryptography, to verify that the message:
- Was indeed sent by your domain
- Has not been modified during transmission
Using DKIM improves email integrity and helps with deliverability by increasing trust in your domain.
Domain-based Message Authentication, Reporting and Conformance (DMARC)
DMARC builds on SPF and DKIM by letting domain owners specify how unauthenticated emails should be handled. It enforces rules such as requiring messages to pass SPF and DKIM checks and tells receiving servers whether to:
- Accept the message
- Quarantine it as suspicious
- Reject it entirely
DMARC also enables reporting, allowing you to monitor who is sending mail using your domain and detect any abuse.
How are SPF, DKIM and DMARC Configured?
These authentication methods are implemented by publishing specific DNS records for your domain:
- SPF: A TXT record listing authorized sending servers
- DKIM: A public key as a TXT record, used to verify DKIM-signed emails
- DMARC: A TXT record defines how to handle unauthenticated email and where to send reports
Correct configuration and maintenance of these DNS records is essential for email security and deliverability.
Conclusion
Implementing SPF, DKIM and DMARC is an important step for protecting your domain from email spoofing, improving deliverability and maintaining trust with recipients. While each protocol serves a different function, they work best when deployed together as part of a comprehensive email authentication strategy. Regularly reviewing and updating these settings ensures your email infrastructure stays secure and effective.