What are SPF, DKIM, and DMARC, and when are they needed?

Summary

SPF, DKIM, and DMARC are crucial email authentication methods that enhance deliverability, protect sender reputation, and prevent spoofing and phishing. SPF specifies authorized mail servers, DKIM adds a digital signature, and DMARC instructs recipient servers on handling authentication failures and offers reporting. Implementing these protocols, especially DMARC, should be carefully considered due to potential setup costs and the risk of blocking legitimate emails. Correct configuration, alignment of visible 'from' addresses, and monitoring DMARC reports are also important.

Key findings

  • SPF Definition: SPF defines which IPs are authorized to send mail on behalf of a domain.
  • DKIM Definition: DKIM adds a digital signature to emails, verifying authenticity and preventing tampering.
  • DMARC Definition: DMARC instructs recipient servers on how to handle emails that fail SPF and DKIM checks and offers reporting.
  • Authentication Importance: These mechanisms are essential for verifying email authenticity and preventing various threats.
  • Deliverability Improvement: SPF, DKIM, and DMARC enhance email deliverability and sender reputation.
  • DMARC as a Tie-in: DMARC ties the visible 'from' address to authentication results.
  • DMARC Reporting: DMARC offers a reporting mechanism which allows domain owners to receive reports about email authentication results.

Key considerations

  • Implementation Timing: Implement SPF, DKIM, and DMARC when sending emails from your own domain.
  • Cost-Benefit Analysis: Evaluate the cost and complexity of setting up DMARC against the potential benefits.
  • Configuration Accuracy: Ensure accurate configuration of SPF records and alignment with the visible 'from' address.
  • DMARC Reporting Monitoring: Monitor DMARC reports to refine authentication policies and address spoofing attempts.
  • Potential Blocking Risk: Recognize the risk of DMARC causing legitimate emails to be blocked and adjust accordingly.

What email marketers say
9Marketer opinions

SPF, DKIM, and DMARC are email authentication methods essential for improving deliverability, protecting sender reputation, and preventing spoofing and phishing attacks. SPF specifies authorized sending IPs, DKIM adds a digital signature to verify message authenticity, and DMARC instructs recipient servers on handling authentication failures and provides reporting. Implementation is crucial when sending emails from your own domain, aligning with visible 'from' addresses, and protecting against email-based cyberattacks.

Key opinions

  • SPF Definition: SPF defines which IPs are allowed to send mail on behalf of a domain.
  • DKIM Definition: DKIM adds a digital signature to emails, verifying authenticity and preventing tampering.
  • DMARC Definition: DMARC instructs recipient servers on how to handle emails that fail SPF and DKIM checks.
  • Deliverability Improvement: SPF, DKIM, and DMARC improve email deliverability and sender reputation.
  • Phishing Prevention: These authentication methods prevent spoofing and phishing attacks.
  • Domain Protection: DMARC specifically ties the visible 'from' address to authentication results.

Key considerations

  • Implementation Timing: Implement SPF, DKIM, and DMARC as soon as you start sending emails from your own domain.
  • Alignment Importance: Align SPF and DKIM with the visible 'from' address for optimal DMARC effectiveness.
  • Comprehensive Protection: These methods provide a comprehensive framework for email authentication and cyberattack prevention.
  • Reputation Management: Using SPF, DKIM, and DMARC helps avoid the spam folder and maintain a positive sender reputation.
Marketer view

Marketer from Email Geeks explains DMARC is the only authentication method that explicitly ties "me" to the visible from-address seen by end users, emphasizing the importance of aligning SPF and DKIM with the visible address.

May 2024 - Email Geeks
Marketer view

Email marketer from Reddit shares that DKIM is needed because it adds a digital signature to your emails, proving that the email truly came from your domain and hasn't been altered in transit. This helps build trust with email providers and improves deliverability.

October 2021 - Reddit
Marketer view

Email marketer from Cloudflare explains that SPF, DKIM, and DMARC are essential because they provide a comprehensive framework for email authentication, improving deliverability, protecting your brand's reputation, and preventing email-based cyberattacks.

January 2023 - Cloudflare
Marketer view

Marketer from Email Geeks explains that SPF is for defining which IPs are allowed to send mail, DKIM is for signing messages to verify authorization, and DMARC specifies what to do with messages that fail SPF and DKIM authentication.

September 2022 - Email Geeks
Marketer view

Email marketer from Proofpoint shares that Implementing DMARC is important to protect your customers, partners, and employees from phishing attacks that spoof your domain name.

April 2024 - Proofpoint
Marketer view

Email marketer from Sendinblue explains that SPF, DKIM, and DMARC are needed as soon as you start sending emails from your own domain, especially for marketing or transactional emails. They're essential for avoiding the spam folder and maintaining a positive sender reputation.

August 2021 - Sendinblue
Marketer view

Email marketer from Mailjet shares that SPF, DKIM, and DMARC are needed to improve email deliverability and protect your domain's reputation by preventing spoofing and phishing attacks. Implementing these protocols builds trust with email providers.

December 2024 - Mailjet
Marketer view

Email marketer from Email Marketing Forum explains that DMARC is needed to specify what recipient mail servers should do with emails that fail SPF and DKIM checks. This helps prevent phishing attacks by instructing servers to reject or quarantine unauthenticated emails.

July 2021 - Email Marketing Forum
Marketer view

Email marketer from SparkPost shares that SPF should be implemented to specify which mail servers are authorized to send emails on behalf of your domain, preventing unauthorized senders from using your domain to send spam or phishing emails. This ensures email is correctly identified.

July 2021 - SparkPost

What the experts say
3Expert opinions

SPF, DKIM, and DMARC are email authentication mechanisms vital for verifying the authenticity of email messages and protecting senders and recipients from spam, phishing, and spoofing. While DMARC offers enhanced protection, its setup can be complex and costly, potentially leading to legitimate emails being blocked. Therefore, carefully evaluate the necessity and potential impact of implementing DMARC.

Key opinions

  • Authentication Mechanisms: SPF, DKIM, and DMARC are mechanisms designed to verify the authenticity of email messages.
  • DMARC Protection: DMARC helps protect email senders and recipients from spam, phishing, and spoofing.
  • DMARC Complexity: DMARC setup can be complex and expensive.
  • DMARC Reporting: DMARC offers a reporting mechanism which allows domain owners to receive reports about email authentication results

Key considerations

  • Cost-Benefit Analysis: Evaluate the cost and complexity of setting up DMARC against the potential benefits.
  • Potential Blocking: Be aware that DMARC implementation might cause legitimate emails to be blocked.
  • BIMI Relevance: Consider DMARC's necessity, particularly if you are considering BIMI (Brand Indicators for Message Identification).
Expert view

Expert from Word to the Wise explains that DMARC is a domain authentication protocol that helps protect email senders and recipients from spam, phishing, and spoofing.

July 2023 - Word to the Wise
Expert view

Expert from SpamResource.com explains that SPF, DKIM, and DMARC are mechanisms to verify the authenticity of email messages and provides a breakdown for each record and their purpose.

September 2022 - SpamResource.com
Expert view

Expert from Email Geeks shares that DMARC can be expensive to set up correctly and might cause wanted mail to be blocked and suggests evaluating its necessity, especially if considering BIMI.

January 2022 - Email Geeks

What the documentation says
6Technical articles

SPF, DKIM, and DMARC are email authentication standards. SPF is a DNS record specifying authorized mail servers to prevent 'From' address forgery. DKIM adds a digital signature for verifying message authenticity and preventing tampering. DMARC builds upon SPF and DKIM, instructing recipient servers on handling failed authentication attempts and providing reporting mechanisms. DMARC also offers reporting, enabling domain owners to refine authentication policies. Proper SPF configuration requires understanding record syntax, and DKIM requires balancing key size for security and system compatibility.

Key findings

  • SPF Definition: SPF is a DNS record listing authorized mail servers to prevent spoofing.
  • DKIM Definition: DKIM adds a digital signature for message authenticity verification.
  • DMARC Definition: DMARC builds on SPF and DKIM, instructing on handling authentication failures and provides reports.
  • DMARC Reporting: DMARC reporting provides insights into spoofing attempts for policy refinement.
  • SPF Syntax: SPF records require understanding specific syntax for configuration.
  • DKIM Key Size: DKIM key size impacts security and system compatibility.

Key considerations

  • SPF Configuration: Properly configure SPF records with correct syntax to authorize sending sources.
  • DKIM Key Size Balance: Balance DKIM key size between security and compatibility with older systems.
  • DMARC Monitoring: Utilize DMARC reports to monitor authentication results and refine policies.
Technical article

Documentation from EasyDMARC explains that DMARC offers a reporting mechanism which allows domain owners to receive reports about email authentication results, providing insights into potential spoofing attempts and helping refine their email authentication policies.

May 2022 - EasyDMARC
Technical article

Documentation from Google explains that SPF (Sender Policy Framework) is a DNS record that lists the mail servers authorized to send email from your domain. It helps prevent spammers from forging the 'From' address on your emails.

December 2023 - Google
Technical article

Documentation from AuthSMTP explains that SPF records use a specific syntax to define authorized sending sources, including IP addresses, domain names, and mechanisms like 'include:' to reference other SPF records. Understanding this syntax is crucial for proper SPF configuration.

November 2024 - AuthSMTP
Technical article

Documentation from DMARC.org explains that DKIM (DomainKeys Identified Mail) adds a digital signature to outgoing email, allowing recipient servers to verify the message's authenticity and that it hasn't been tampered with during transit.

September 2023 - DMARC.org
Technical article

Documentation from Microsoft explains that DMARC (Domain-based Message Authentication, Reporting & Conformance) builds on SPF and DKIM to provide instructions to recipient mail servers on how to handle emails that fail authentication checks. It also provides reporting mechanisms.

May 2024 - Microsoft
Technical article

Documentation from Port25 explains that DKIM key size is an important aspect of DKIM configuration, larger key sizes generally provide stronger security, but it's important to balance security with compatibility as some older systems may not support the largest key sizes.

July 2022 - Port25