--- title: "What is the Difference Between DomainKeys and DKIM? | DuoCircle" description: "What is the Difference Between DomainKeys and DKIM?" image: "https://www.duocircle.com/images/og-default.png" canonical: "https://www.duocircle.com/blog/email-security/what-is-the-difference-between-domainkeys-and-dkim/" --- Quick Answer DomainKeys was an email authentication protocol developed by Yahoo in 2004 that signed outgoing messages with a private key matched to a public key in DNS. DKIM (DomainKeys Identified Mail) is its successor, formed in 2004 by merging DomainKeys with Cisco's Identified Internet Mail (IIM). DomainKeys is deprecated and no longer in active use. The differences: DKIM uses an open IETF standard (RFC 6376) for broad interoperability; supports multiple selectors so a domain can rotate keys and have many simultaneously; signs a configurable list of headers; and forms the basis of DMARC alignment. If you encounter a DomainKeys reference today (the legacy DomainKey-Signature header), it is historical. Use DKIM. What is the Difference Between DomainKeys and DKIM? Your browser does not support the audio element. [ Download episode](https://media.mailhop.org/duocircle/images/2024/04/What-is-the-Difference-Between-DomainKeys-and-DKIM.mp3) Share [ ](https://www.linkedin.com/sharing/share-offsite/?url=undefined%2Fblog%2Femail-security%2Fwhat-is-the-difference-between-domainkeys-and-dkim%2F "Share on LinkedIn") [ ](https://twitter.com/intent/tweet?text=What%20is%20the%20Difference%20Between%20DomainKeys%20and%20DKIM%3F&url=undefined%2Fblog%2Femail-security%2Fwhat-is-the-difference-between-domainkeys-and-dkim%2F "Share on X/Twitter") [ ](https://www.facebook.com/sharer/sharer.php?u=undefined%2Fblog%2Femail-security%2Fwhat-is-the-difference-between-domainkeys-and-dkim%2F "Share on Facebook") [ ](https://reddit.com/submit?url=undefined%2Fblog%2Femail-security%2Fwhat-is-the-difference-between-domainkeys-and-dkim%2F&title=What%20is%20the%20Difference%20Between%20DomainKeys%20and%20DKIM%3F "Share on Reddit") [ ](mailto:?subject=What%20is%20the%20Difference%20Between%20DomainKeys%20and%20DKIM%3F&body=Check out this article: undefined%2Fblog%2Femail-security%2Fwhat-is-the-difference-between-domainkeys-and-dkim%2F "Share via Email") ![DomainKeys and DKIM](https://media.mailhop.org/duocircle/images/2024/04/sendgrid-alternative-4968.jpg) Both these terms sound alike, so some people get confused and use them interchangeably. However, doing so isn’t right. [DKIM](/resources/what-is-dkim), which stands for DomainKeys Identified Mail, is a **successor to Yahoo’s DomainKey or DK**. To understand this better, we’ll have to **rewind a little** to the past. In the early 2000s, industry experts recognized the need to improve [email security](/) to combat email-based frauds and spam while fostering **trust and reliability** in email communication. To achieve this goal, a proposal was made in 2004 to combine Yahoo’s DomainKeys and **Cisco’s Identified Internet Mail (IIM)** to form the DKIM standard. While the protocols serve similar purposes, they have some key differences. **DomainKeys is now obsolete** and has been replaced by DKIM. ## What is DomainKeys? DomainKeys is a deprecated [email authentication](/resources/email-authentication) protocol **developed by Yahoo**. _It worked by adding a digital signature to the email message header using public-key cryptography_. This signature was generated using a private key that corresponded to a public key stored in the openly accessible DNS records of the sender. ## What is DomainKeys Identified Mail or DKIM? DKIM also resolves the same purpose but **uses an open standard**, making it simpler for email service providers to interpret and interoperate efficiently. DKIM also attaches a digital signature to the email header using [public key cryptography](https://en.wikipedia.org/wiki/Public-key%5Fcryptography). [![DMARC adoption](https://media.mailhop.org/duocircle/images/2024/04/windows-smtp-service-2.jpg)](https://media.mailhop.org/duocircle/images/2024/04/windows-smtp-service-2.jpg) ## The Key Differences Both technologies had **similar objectives** of verifying the [senders’ authenticity](/email-services/learning-to-trace-back-emails-to-their-source-ip-addresses/) but involved different approaches and implementations. By merging these technologies, the developers could leverage the strengths of each approach and create a more comprehensive solution. So, let’s see what differences they have. ### 1\. History and Development #### DomainKeys It was created by Yahoo in 2004 **in collaboration with Cisco** and was one of the earliest attempts to [secure email](/email-security/ensure-confidentiality-of-your-emails-with-secure-email-gateways-and-end-to-end-encryption/) through sender authentication. #### DKIM DKIM was the successor and **evolved version of DomainKeys**, which was developed by a consortium of tech giants, including [Yahoo](/email-services/google-yahoo-mandatory-to-deploy-dmarc-for-more-than-5000-daily-emails/), Cisco, Microsoft, etc. It was made public in 2007. ### 2\. Keys #### DomainKeys This method involved the **use of a single private key** that the sender uses to add a [digital signature](https://www.techtarget.com/searchsecurity/definition/digital-signature) to an outgoing email. The corresponding public key was published in the DNS records of the sending domain. #### DKIM DKIM uses a **pair of keys**, a private key for signing outgoing emails and a public key published in the [DNS records](/data-privacy/dns-record-types-defined-and-explained/) of the sending domain. ### 3\. Signature Placement #### DomainKeys The digital signature was added to the **entire message body** and selected headers. #### DKIM _[DKIM offers the flexibility](/email-hosting/what-is-dkim-and-why-you-should-use-it-to-secure-your-email/) in selecting which parts of an email to sign_. It can sign **specific headers, the body, or both**. ### 4\. Compatibility #### DomainKeys DomainKeys had **limited adoption** and is largely deprecated in favor of DKIM. #### DKIM DKIM is **widely adopted and supported** by major email providers and servers, becoming the [de facto standard](https://en.wikipedia.org/wiki/De%5Ffacto%5Fstandard) for email authentication. [![email-based spamming](https://media.mailhop.org/duocircle/images/2024/04/spf-record-checker-3850.jpg)](https://media.mailhop.org/duocircle/images/2024/04/spf-record-checker-3850.jpg) ### 5\. Security Features #### DomainKeys DomainKeys prevented [email-based spamming](https://www.bleepingcomputer.com/news/security/hijacked-subdomains-of-major-brands-used-in-massive-spam-campaign/), spoofing, and phishing attempts. #### DKIM In addition to preventing email-based spamming, spoofing, and [phishing attempts](https://gbhackers.com/microsoft-two-step-phishing-campaign/), DKIM has the ability to include a [hash of the message body](https://blog.getadmiral.com/hashed-emails-what-publishers-should-know-about-this-identity-solution) in the signature. This allows verification of the **integrity of the email’s content**. [SPF](/content/spf-record-check), DKIM, and [DMARC](/email/dmarc) combat email-based menaces and **largely compensate** for each other’s shortcomings, becoming a wholesome combination. ## Topics email headeremail securityTrends ![Brad Slavin](https://media.mailhop.org/dmarcreport/images/team/brad-slavin.jpg) Brad Slavin General Manager General Manager at DuoCircle. Product strategy and commercial lead across the email security portfolio. ## Secure your email infrastructure Protect, authenticate, and deliver. Contact our team to find the right solution. [Contact Sales](/contact/) [Explore Products](/products/) ## Related Articles [ Email Security 6m 5 Reasons Why Your Website Needs an SPF Record Flattener? Sep 26, 2023 ](/blog/email-security/5-reasons-why-your-website-needs-an-spf-record-flattener/)[ Email Security 10m 7 Best Practices for Email Security and Compliance in Financial Services Jan 21, 2026 ](/blog/email-security/7-best-practices-for-email-security-and-compliance-in-financial-services/)[ Email Security 3m What are the best practices to follow for managing DKIM keys? Oct 25, 2024 ](/blog/email-security/best-practices-to-follow-for-managing-dkim-keys/)[ Email Security 6m Decoding Canonicalization: The Reason Behind DKIM Signature Verification Failures May 2, 2024 ](/blog/email-security/canonicalization-reason-behind-dkim-signature-verification-failures/) ```json {"@context":"https://schema.org","@type":"Organization","name":"DuoCircle LLC","url":"https://www.duocircle.com","logo":{"@type":"ImageObject","url":"https://www.duocircle.com/images/duocircle-logo.png"},"description":"DuoCircle is a portfolio of specialized email products covering protection, authentication, delivery, and routing. We deliver about 90% of category-leader capability at roughly half the price, backed by experts who own the outcome. 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