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Understanding Email Authentication
What is Email Authentication?
Email authentication is a collection of techniques and protocols designed to verify the legitimacy of email messages. The three core protocols - SPF, DKIM, and DMARC - work together to prevent email spoofing, reduce spam, and protect your domain reputation.
SPF (Sender Policy Framework)
SPF allows domain owners to specify which mail servers are authorized to send email on behalf of their domain. When a receiving server gets an email, it checks the SPF record in DNS to verify the sender is authorized. SPF records are TXT records in DNS that list allowed IP addresses and domains.
DKIM (DomainKeys Identified Mail)
DKIM adds a digital signature to every email sent from your domain. This signature is created using a private key held by the sending server and can be verified using a public key published in DNS. DKIM ensures the email has not been modified in transit and confirms it was authorized by the domain owner.
DMARC (Domain-based Message Authentication)
DMARC builds on SPF and DKIM by telling receiving servers what to do when an email fails authentication checks. It also provides a reporting mechanism so domain owners can monitor authentication failures and identify potential spoofing attempts. DMARC policies can be set to none (monitoring only), quarantine (mark as spam), or reject (block delivery).
Why Email Authentication Matters
Email authentication protects your brand and recipients from phishing attacks, prevents your domain from being used by spammers, improves email deliverability rates, and builds trust with email providers and recipients. Major email providers like Gmail and Yahoo now require DMARC for bulk senders.
Best Practices
Start by implementing SPF and DKIM for all sending sources. Add DMARC in monitoring mode (p=none) to collect data without affecting delivery. Review DMARC reports to identify legitimate senders and fix authentication issues. Gradually increase DMARC policy enforcement to quarantine and then reject. Keep your SPF record under the 10 DNS lookup limit. Use strong DKIM keys (2048-bit RSA). Rotate DKIM keys periodically for security.
Frequently Asked Questions
Common questions about the Email Authentication Validator
Email authentication is a set of protocols (SPF, DKIM, DMARC) used to verify that emails are legitimately sent from your domain and have not been tampered with. These protocols help prevent email spoofing, phishing, and ensure deliverability.
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