--- title: "What is GAPPSSMTP and How to Set Up a Custom DKIM Key For Your Emails? | DMARC Report" description: "What is GAPPSSMTP and How to Set Up a Custom DKIM Key For Your Emails? from DMARC Report explains practical steps for email authentication, domain." image: "https://dmarcreport.com/og/blog/what-is-gappssmtp-and-how-to-set-up-a-custom-dkim-key-for-your-emails.png" canonical: "https://dmarcreport.com/blog/what-is-gappssmtp-and-how-to-set-up-a-custom-dkim-key-for-your-emails/" --- Quick Answer \[DMARC Report\](https://soundcloud.com/dmarcreport-1-325699943) · \[What is GAPPSSMTP and How to Set Up a Custom DKIM Key For Your Emails?\](https://soundcloud.com/dmarcreport-1-325699943/what-is-gappssmtp-and-how-to-set-up-a-custom-dkim-key-for-your-emails) Related: [Free DMARC Checker](/tools/dmarc-checker/) Share [ ](https://www.linkedin.com/sharing/share-offsite/?url=undefined%2Fblog%2Fwhat-is-gappssmtp-and-how-to-set-up-a-custom-dkim-key-for-your-emails%2F "Share on LinkedIn") [ ](https://twitter.com/intent/tweet?text=What%20is%20GAPPSSMTP%20and%20How%20to%20Set%20Up%20a%20Custom%20DKIM%20Key%20For%20Your%20Emails%3F&url=undefined%2Fblog%2Fwhat-is-gappssmtp-and-how-to-set-up-a-custom-dkim-key-for-your-emails%2F "Share on X/Twitter") [ ](https://www.facebook.com/sharer/sharer.php?u=undefined%2Fblog%2Fwhat-is-gappssmtp-and-how-to-set-up-a-custom-dkim-key-for-your-emails%2F "Share on Facebook") [ ](https://reddit.com/submit?url=undefined%2Fblog%2Fwhat-is-gappssmtp-and-how-to-set-up-a-custom-dkim-key-for-your-emails%2F&title=What%20is%20GAPPSSMTP%20and%20How%20to%20Set%20Up%20a%20Custom%20DKIM%20Key%20For%20Your%20Emails%3F "Share on Reddit") [ ](mailto:?subject=What%20is%20GAPPSSMTP%20and%20How%20to%20Set%20Up%20a%20Custom%20DKIM%20Key%20For%20Your%20Emails%3F&body=Check out this article: undefined%2Fblog%2Fwhat-is-gappssmtp-and-how-to-set-up-a-custom-dkim-key-for-your-emails%2F "Share via Email") ![What is GAPPSSMTP and How to Set Up a Custom DKIM Key For Your Emails?](https://media.mailhop.org/dmarcreport/images/2022/04/dmarc-alignment-6379.jpg) ## Try Our Free DKIM Lookup Auto-discover DKIM selectors for any domain - scan 185 common selectors across all major providers. [ Discover DKIM Selectors → ](/tools/dkim-lookup/) > DKIM is the authentication protocol that survives email forwarding, says Brad Slavin, General Manager of DuoCircle. When SPF fails because a forwarder’s IP isn’t in the original record, DKIM alignment is the only path to DMARC pass. That’s why we monitor DKIM alongside SPF in every DMARC Report dashboard. DKIM ([RFC 6376](https://datatracker.ietf.org/doc/html/rfc6376)) signs email messages cryptographically, and unlike SPF, the signature survives email forwarding - which is why DMARC alignment via DKIM is more reliable than SPF alignment for forwarded mail and mailing lists.[DMARC Report](https://soundcloud.com/dmarcreport-1-325699943) · [What is GAPPSSMTP and How to Set Up a Custom DKIM Key For Your Emails?](https://soundcloud.com/dmarcreport-1-325699943/what-is-gappssmtp-and-how-to-set-up-a-custom-dkim-key-for-your-emails) _GAPPSSMTP stands for Google Apps Simple Mail Transfer Protocol, which is responsible for exchanging email messages **securely and swiftly**_. This is a part of Google Workspace’s suite of tools. ## What Is GAPPSSMTP? Every outgoing message that is sent through the [Gmail SMTP server](https://world.siteground.com/kb/gmail-smtp-server/) is signed with a \*\*default DKIM key to prevent [email tampering](https://www.experian.com/blogs/ask-experian/what-is-mail-tampering/) and verify the sender’s authentication. By default, this key is d=\*.gappssmtp.com ; however, users can set a manual [DKIM record](https://dmarcreport.com/blog/dkim-examples-a-comprehensive-guide-to-email-configuration/) in which different keys are generated for the authentication process. Please note that \*\*this is only for email messages sent from Google ; the ones sent from non-Google servers don’t get signed with the default DKIM key. ## DKIM Signatures Help Spot Suspicious Messages Navigate the ‘show details’ drop-down located under the sender’s name column to retrieve the DKIM record linked with the domain from which the potentially phishing message has been dispatched. Check the \*\*‘signed by’ part to verify if it has been sent from [an unsecured server](https://www.trendmicro.com/vinfo/fr/security/news/online-privacy/unsecured-server-leaks-pii-of-almost-90-of-panama-residents). If you see ‘Gmail,’ then the DKIM record will include the **GAPPSSMTP key**, which indicates that it was sent from a secure server . However, emails sent through other Google Apps like Drive, Calendar, Box, etc., don’t have a customer-identified [DKIM](https://dmarcreport.com/what-is-dkim/); hence, they are **automatically signed by GAPPSSMTP**. ![Dmarc report](https://media.mailhop.org/dmarcreport/images/2023/12/dmarc-report-2347.jpg) ## What Are the Differences Between GAPPSSMTP and DKIM? \*\*GAPPSSMTPDKIMPurpose It’s a protocol provided \*\*by Google for sending emails through Gmail. DKIM is a method for validating the authenticity of an email message \*\*by associating a domain name with the message. \*\*Functionality When you configure your email client or application to use Gmail SMTP settings, it allows you to send emails using your \*\*Gmail account through the [SMTP protocol](https://www.geeksforgeeks.org/simple-mail-transfer-protocol-smtp/). When an email is sent with DKIM, the sending mail server adds a [digital signature](https://en.wikipedia.org/wiki/Digital%5Fsignature) to the email header. The receiving mail server can then use the public key published in the sender’s DNS records to verify the signature, confirming that the claimed domain indeed sent the email and that it \*\*hasn’t been tampered with during transit. \*\*Authentication To use Gmail SMTP, you typically need to provide your Gmail username and password and sometimes enable ” less secure app access ” in your Google account settings. This ensures that \*\*only authorized users can send emails using your Gmail account. DKIM helps prevent [email spoofing](https://www.infosecurity-magazine.com/news/bec-attacks-spoof-ccd-execs-force/) and phishing by allowing the recipient’s email server to verify that the claimed sender actually sent the email. ## How Do You Configure a Custom DKIM Key? As aforementioned, emails sent from email service providers other than Google don’t sign outgoing messages using the default DKIM keys. So, you can use the following steps to configure a **custom DKIM key**: - Sign in as a super administrator. - Then turn on Gmail for your domain. It’s recommended to wait for \*\*24-72 hours to have your DKIM record show up. Otherwise, you might encounter the ‘ DKIM record not created’ error . - sign in to your Google Admin console and navigate to Menu > Apps > Google Workspace > Gmail. Next, click on ‘**Authenticate Email**’ and select the domain for which you want to [configure DKIM](https://dmarcreport.com/blog/dkim-best-practices-essential-guidelines-for-email-authentication/). - Navigate to an option where you can produce a \*\*new record and configure DKIM key settings, which allows you to select the bit length of keys . Remember, the lengthier the keys, the more challenging it is for hackers to break them. - **Select a prefix**. The default one is ‘Google’, which is recommended for use. If your domain already utilizes a DKIM key with the prefix “google,” enter a different prefix in this field. - Look for the ‘“Generate new record” box and click on ‘Generate.’ On the configuration page, the text string beneath the “**TXT record value**” section will be updated with a new value, and you will receive a confirmation message stating, “[DKIM authentication](https://dmarcreport.com/blog/dkim-explained-how-dkim-works-and-why-is-dkim-important-for-organizations/) settings have been updated.” - Subsequently, proceed to \*\*copy the DKIM values and insert the DKIM record into your domain. ## How Do You Deploy DKIM? Go to your Google Admin console and follow these steps- - Go to “Menu,” then “Apps,” proceed to “**Google Workspace**,” and finally select “Gmail.” - Click on “Authenticate email.” - From the “Selected domain” dropdown menu, choose the domain for which you wish to enable DKIM. - Click the “Start authentication” button. Upon successful completion of [DKIM setup](https://dmarcreport.com/blog/how-to-check-if-your-email-authentication-is-set-up-correctly-for-dkim-dmarc-spf-bimi/) and proper functionality, the status at the top of the page will change to: “Authenticating email with DKIM.” ![Dmarc analyzer](https://media.mailhop.org/dmarcreport/images/2023/12/dmarc-analyzer-7896.jpg) ## Summary In summary, GAPPSSMTP is about the protocol and settings used for sending emails through Gmail, while DKIM, in combination with [SPF](https://dmarcreport.com/what-is-spf/) and [DMARC](https://dmarcreport.com/), provides a robust framework for verifying the authenticity of email messages. Specifically, DKIM ensures the integrity of emails by \*\*digitally signing them using a private key. This allows recipients to confirm the signature’s validity using a corresponding [public k](https://www.coursera.org/articles/public-key)[ey](https://www.coursera.org/articles/public-key) that is stored in DNS records. When integrated with SPF and [DMARC protocols](https://dmarcreport.com/blog/what-is-a-dmarc-record-and-why-you-need-it/), this enhances the overall security measure, providing a more trustworthy email communication environment. They are complementary in the sense that you can use GAPPSSMTP to send emails, and DKIM can be employed to enhance [email authentication](https://dmarcreport.com/blog/spf-vs-dkim-vs-dmarc-difference-explained-2026/) and security. Together, they can fortify [email-based menaces](https://microage.ca/13-email-threat-types-to-know-about-right-now/). ## Topics [ dkim ](/tags/dkim/)[ DKIM key ](/tags/dkim-key/)[ DMARC ](/tags/dmarc/)[ email security ](/tags/email-security/) ![Vishal Lamba](https://media.mailhop.org/dmarcreport/images/team/vishal-lamba.jpg) [ Vishal Lamba ](/authors/vishal-lamba/) Content Specialist Content Specialist at DMARC Report. Writes vendor-specific email authentication guides and troubleshooting walkthroughs. [LinkedIn Profile →](https://www.linkedin.com/in/vishal-lamba/) ## Take control of your DMARC reports Turn raw XML into actionable dashboards. Start free - no credit card required. [Start Free Trial](https://app.dmarcreport.com/) [Check Your DMARC Record](/tools/dmarc-checker/) ## Related Articles [ Intermediate 8m Decoding I-Tag DKIM Vulnerability and Its Impact on Email Deliverability and Security Jun 6, 2024 ](/blog/decoding-i-tag-dkim-vulnerability-and-its-impact-on-email-security/)[ Intermediate 4m Getting Rid of Common SPF Errors for Email Security and Delivery Dec 20, 2023 ](/blog/getting-rid-of-common-spf-errors-for-email-security-and-delivery/)[ Intermediate 3m The Emergence of DKIM: A Cryptography-Based Email Authentication Protocol Nov 29, 2023 ](/blog/the-emergence-of-dkim-a-cryptography-based-email-authentication-protocol/)[ Intermediate 5m What is a DKIM Replay Attack and How to Prevent it? 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