--- title: "Know these Gmail SMTP error codes to fix email delivery issues for your company’s domain | DuoCircle" description: "Know these Gmail SMTP error codes to fix email delivery issues for your company’s domain." image: "https://www.duocircle.com/images/og-default.png" canonical: "https://www.duocircle.com/blog/outbound-smtp/gmail-smtp-error-codes-resolve-your-companys-email-delivery-issues/" --- Quick Answer Gmail SMTP error codes are three digits: the first (1 to 5) indicates the response class, the second indicates the issue type (syntax, connection), and the third gives mail-transfer specifics. Three common Gmail rejections: \`550 5.7.26\` means the message failed SPF and/or DKIM. Causes include multiple SPF records, wrong syntax, sending IP not in SPF, invalid or missing DKIM record, or sending the same message to too many recipients. Fix with lookup tools, correct DKIM, and a reputable mail server. \`550 5.2.1\` means the recipient mailbox is over capacity or rate-limited; verify the recipient address, batch large sends, and respect the recipient's email policy. \`550 5.4.5\` means the daily sending limit was exceeded. Gmail caps SMTP at 100/day, web at 500/day, and POP/IMAP clients like Outlook at 100/day; wait 24 hours for the account to re-enable, or use an SMTP relay service for higher volume. Know these Gmail SMTP error codes to fix email delivery issues for your company’s domain Your browser does not support the audio element. [ Download episode](https://media.mailhop.org/duocircle/images/2024/07/Know-These-Gmail-SMTP-Error-Codes-To-Fix-Email-Delivery-Issues-For-Your-Companys-Domain.mp3) Share [ ](https://www.linkedin.com/sharing/share-offsite/?url=undefined%2Fblog%2Foutbound-smtp%2Fgmail-smtp-error-codes-resolve-your-companys-email-delivery-issues%2F "Share on LinkedIn") [ ](https://twitter.com/intent/tweet?text=Know%20these%20Gmail%20SMTP%20error%20codes%20to%20fix%20email%20delivery%20issues%20for%20your%20company%E2%80%99s%20domain&url=undefined%2Fblog%2Foutbound-smtp%2Fgmail-smtp-error-codes-resolve-your-companys-email-delivery-issues%2F "Share on X/Twitter") [ ](https://www.facebook.com/sharer/sharer.php?u=undefined%2Fblog%2Foutbound-smtp%2Fgmail-smtp-error-codes-resolve-your-companys-email-delivery-issues%2F "Share on Facebook") [ ](https://reddit.com/submit?url=undefined%2Fblog%2Foutbound-smtp%2Fgmail-smtp-error-codes-resolve-your-companys-email-delivery-issues%2F&title=Know%20these%20Gmail%20SMTP%20error%20codes%20to%20fix%20email%20delivery%20issues%20for%20your%20company%E2%80%99s%20domain "Share on Reddit") [ ](mailto:?subject=Know%20these%20Gmail%20SMTP%20error%20codes%20to%20fix%20email%20delivery%20issues%20for%20your%20company%E2%80%99s%20domain&body=Check out this article: undefined%2Fblog%2Foutbound-smtp%2Fgmail-smtp-error-codes-resolve-your-companys-email-delivery-issues%2F "Share via Email") ![SMTP error codes to fix email delivery](https://media.mailhop.org/duocircle/images/2024/07/phishing-protection-5051.jpg) Not all your emails pass authentication checks and other filters, thus returning with [error codes](https://en.wikipedia.org/wiki/Error%5Fcode). These codes help **diagnose and understand issues** that occurred during email transmission, letting you fix them and resend the message. _For instance, it could indicate if the problem is due to incorrect credentials, a blocked email, or a temporary server issue._ Some error codes indicate **security-related issues**, such as [failed authentication](/dmarc/causes-and-solutions-of-dmarc-failures/) attempts or detection of spam or [phishing attempts](https://www.infosecurity-magazine.com/news/341-rise-advanced-phishing-attacks/). Here we are listing the most commonly encountered **error codes in Gmail** and ways to fix them. ## How to read Gmail SMTP error codes? An SMTP error code is a three-digit number. The first digit (1-5) shows the **server’s response** to the command, whether it accepted or encountered an error. The second digit indicates the **type of issue**, like a syntax or connection problem. The **third digit provides specific details** about the mail transfer status. ## Common Gmail SMTP error codes ### ERROR CODE- 550, “5.7.26” This error code is returned when your email fails [SPF](/content/spf-record-check) and/or [DKIM checks](/email-services/gmail-550-5-7-26-error-for-emails-failing-dmarc-checks/). The possible reasons for this failure are- - **Multiple SPF records** found for your sending domain. - Inclusion of wrong SPF and DKIM **syntax**. - The sender’s IP address is not listed in the [SPF record](/content/spf-records). - Invalid or incomplete [DKIM record](https://support.dnsimple.com/articles/dkim-record/). - Sending the same email to too many recipients at once. This is considered a [spam-y behavior](https://en.wikipedia.org/wiki/Spamming). [![Multiple SPF records](https://media.mailhop.org/duocircle/images/2024/07/anti-phishing-software-5052.jpg)](https://media.mailhop.org/duocircle/images/2024/07/anti-phishing-software-5052.jpg) Here’s how you can **resolve these issues**\- - _Using **lookup tools** to see configurational and syntactical issues._ - Adding DKIM information to the sender’s email. - Switching to a [reputed email server](https://emailmastery.org/email-marketing-glossary/email-server/). ### ERROR CODE- 550, “5.2.1” Gmail returns this error code when a recipient’s mailbox **receives a lot of emails** at once. This error prompts when the recipient has many unread emails lying in their inbox. Here’s how you can resolve this issue- - **Recheck and ensure** you have entered the correct email address in the ‘To;’ field. - Avoid sending emails to a lot of recipients at once. - **Break large emails** into multiple small emails. - Comply with the recipient’s [email policy](https://www.zoho.com/mail/glossary/email-policy.html). ### ERROR CODE- 550, “5.4.5” This error code prompts when you **exceed the daily sending limit**. _Gmail enforces [daily sending limits](https://www.close.com/blog/gmail-sending-limits) to manage email traffic and prevent abuse._ For [SMTP](/content/smtp-email) delivery, the **daily quota is set at 100 emails**. When using the web interface, users can send up to 500 emails per day. For those using [POP or IMAP clients](https://support.google.com/a/answer/12103?hl=en), such as [Microsoft Outlook](/email-archiving/email-archiving-integration-with-microsoft-outlook-enhances-data-management/), the maximum limit for sending emails at once is capped at 100. Here’s how the issue can be fixed- - **Send emails after 24 hours**. If your account is temporarily disabled, it will be automatically enabled after 24 hours of reaching the daily limit. - Contact your administrator or refer to the [SMTP relay service](/content/smtp-relay-service) error message if you wish to get your daily email allowance exceeded. [![SMTP Server](https://media.mailhop.org/duocircle/images/2024/07/SPF-record-checker-2.jpg)](https://media.mailhop.org/duocircle/images/2024/07/SPF-record-checker-2.jpg) ## Final words Understanding [SMTP error codes](https://en.wikipedia.org/wiki/List%5Fof%5FSMTP%5Fserver%5Freturn%5Fcodes) helps diagnose and **resolve email delivery issues**, highlighting the complexity of digital communication and the importance of [email security](/). These codes, often considered technical jargon, are crucial in ensuring messages reach their destinations. ## Topics SecurityUpdates ![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 [ SMTP 6m How to solve the “550 5.7.0 Local Policy Violation” error Jan 1, 2026 ](/blog/outbound-smtp/how-to-solve-the-550-5-7-0-local-policy-violation-error/)[ News 3m Alert: Fix SPF & DKIM Settings For Your Email Forwarding Set Up Through Microsoft o365 SMTP Server Or Your Emails May End Up In Spam Jul 20, 2021 ](/blog/announcements/alert-fix-spf-dkim-settings-for-your-email-forwarding-set-up-through-microsoft-o365-smtp-server-or-your-emails-may-end-up-in-spam/)[ News 6m Cyber Security News Update, Week 1 of 2022 Jan 7, 2022 ](/blog/announcements/cyber-security-news-update-week-1-of-2022/)[ News 7m Cybersecurity News Update, Week 1 of 2023 Jan 1, 2023 ](/blog/announcements/cyber-security-news-update-week-1-of-2023/) ```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. Trusted by 50,000+ organizations since 2014.","subOrganization":[{"@type":"Organization","@id":"https://www.wikidata.org/wiki/Q138898167","name":"DMARC Report","url":"https://dmarcreport.com"},{"@type":"Organization","@id":"https://www.wikidata.org/wiki/Q138897474","name":"AutoSPF","url":"https://autospf.com"},{"@type":"Organization","@id":"https://www.wikidata.org/wiki/Q138897912","name":"Phish Protection","url":"https://www.phishprotection.com"}],"sameAs":["https://www.linkedin.com/company/duocircle","https://x.com/duocirclellc","https://www.facebook.com/duocirclellc","https://www.g2.com/products/phish-protection-by-duocircle/reviews","https://github.com/duocircle","https://www.crunchbase.com/organization/duocircle-llc"],"contactPoint":{"@type":"ContactPoint","contactType":"customer support","url":"https://support.duocircle.com"},"knowsAbout":["Email Security","Email Authentication","SPF","DKIM","DMARC","Phishing Protection","Spam Filtering","SMTP Relay","Email Deliverability","Email Forwarding"]} ``` ```json {"@context":"https://schema.org","@type":"WebSite","name":"DuoCircle LLC","url":"https://www.duocircle.com","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. Trusted by 50,000+ organizations since 2014.","publisher":{"@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. Trusted by 50,000+ organizations since 2014.","subOrganization":[{"@type":"Organization","@id":"https://www.wikidata.org/wiki/Q138898167","name":"DMARC Report","url":"https://dmarcreport.com"},{"@type":"Organization","@id":"https://www.wikidata.org/wiki/Q138897474","name":"AutoSPF","url":"https://autospf.com"},{"@type":"Organization","@id":"https://www.wikidata.org/wiki/Q138897912","name":"Phish Protection","url":"https://www.phishprotection.com"}]}} ``` ```json [{"@context":"https://schema.org","@type":"BlogPosting","headline":"Know these Gmail SMTP error codes to fix email delivery issues for your company’s domain","description":"Know these Gmail SMTP error codes to fix email delivery issues for your company’s domain.","url":"https://www.duocircle.com/blog/outbound-smtp/gmail-smtp-error-codes-resolve-your-companys-email-delivery-issues/","datePublished":"2024-07-03T10:54:01.000Z","dateModified":"2025-04-24T13:03:33.000Z","dateCreated":"2024-07-03T10:54:01.000Z","author":{"@type":"Person","@id":"https://www.duocircle.com/authors/brad-slavin/#person","name":"Brad Slavin","url":"https://www.duocircle.com/authors/brad-slavin/","jobTitle":"General Manager","description":"Brad Slavin runs DuoCircle, the company behind DMARC Report, AutoSPF, Phish Protection, and Mailhop. His focus is product strategy, customer relationships, and the commercial and compliance side of email authentication (DPAs, SLAs, enterprise procurement).","image":"https://media.mailhop.org/dmarcreport/images/team/brad-slavin.jpg","knowsAbout":["Email Security Strategy","SaaS Product Management","Enterprise Compliance","Customer Success","Email Deliverability Business"],"worksFor":{"@type":"Organization","name":"DuoCircle LLC","url":"https://www.duocircle.com"},"sameAs":["https://www.linkedin.com/in/bradslavin"]},"publisher":{"@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. Trusted by 50,000+ organizations since 2014.","subOrganization":[{"@type":"Organization","@id":"https://www.wikidata.org/wiki/Q138898167","name":"DMARC Report","url":"https://dmarcreport.com"},{"@type":"Organization","@id":"https://www.wikidata.org/wiki/Q138897474","name":"AutoSPF","url":"https://autospf.com"},{"@type":"Organization","@id":"https://www.wikidata.org/wiki/Q138897912","name":"Phish Protection","url":"https://www.phishprotection.com"}]},"mainEntityOfPage":{"@type":"WebPage","@id":"https://www.duocircle.com/blog/outbound-smtp/gmail-smtp-error-codes-resolve-your-companys-email-delivery-issues/"},"articleSection":"outbound-smtp","keywords":"Security, Updates","wordCount":517,"image":{"@type":"ImageObject","url":"https://media.mailhop.org/duocircle/images/2024/07/phishing-protection-5051.jpg","caption":"SMTP error codes to fix email delivery","width":900,"height":600},"speakable":{"@type":"SpeakableSpecification","cssSelector":[".answer-block","h1"]}},{"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Blog","item":"https://www.duocircle.com/blog/"},{"@type":"ListItem","position":2,"name":"SMTP"},{"@type":"ListItem","position":3,"name":"Know these Gmail SMTP error codes to fix email delivery issues for your company’s domain","item":"https://www.duocircle.com/blog/outbound-smtp/gmail-smtp-error-codes-resolve-your-companys-email-delivery-issues/"}]}] ``` ```json {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://www.duocircle.com/"},{"@type":"ListItem","position":2,"name":"Blog","item":"https://www.duocircle.com/blog/"},{"@type":"ListItem","position":3,"name":"SMTP","item":"https://www.duocircle.comundefined"},{"@type":"ListItem","position":4,"name":"Know these Gmail SMTP error codes to fix email delivery issues for your company’s domain","item":"https://www.duocircle.com/blog/outbound-smtp/gmail-smtp-error-codes-resolve-your-companys-email-delivery-issues/"}]} ``` ```json {"@context":"https://schema.org","@type":"BlogPosting","headline":"Know these Gmail SMTP error codes to fix email delivery issues for your company’s domain","description":"Know these Gmail SMTP error codes to fix email delivery issues for your company’s domain.","url":"https://www.duocircle.com/blog/outbound-smtp/gmail-smtp-error-codes-resolve-your-companys-email-delivery-issues/","datePublished":"2024-07-03T10:54:01.000Z","dateModified":"2025-04-24T13:03:33.000Z","dateCreated":"2024-07-03T10:54:01.000Z","author":{"@type":"Person","@id":"https://www.duocircle.com/authors/brad-slavin/#person","name":"Brad Slavin","url":"https://www.duocircle.com/authors/brad-slavin/","jobTitle":"General Manager","description":"Brad Slavin runs DuoCircle, the company behind DMARC Report, AutoSPF, Phish Protection, and Mailhop. His focus is product strategy, customer relationships, and the commercial and compliance side of email authentication (DPAs, SLAs, enterprise procurement).","image":"https://media.mailhop.org/dmarcreport/images/team/brad-slavin.jpg","knowsAbout":["Email Security Strategy","SaaS Product Management","Enterprise Compliance","Customer Success","Email Deliverability Business"],"worksFor":{"@type":"Organization","name":"DuoCircle LLC","url":"https://www.duocircle.com"},"sameAs":["https://www.linkedin.com/in/bradslavin"]},"publisher":{"@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. Trusted by 50,000+ organizations since 2014.","subOrganization":[{"@type":"Organization","@id":"https://www.wikidata.org/wiki/Q138898167","name":"DMARC Report","url":"https://dmarcreport.com"},{"@type":"Organization","@id":"https://www.wikidata.org/wiki/Q138897474","name":"AutoSPF","url":"https://autospf.com"},{"@type":"Organization","@id":"https://www.wikidata.org/wiki/Q138897912","name":"Phish Protection","url":"https://www.phishprotection.com"}]},"mainEntityOfPage":{"@type":"WebPage","@id":"https://www.duocircle.com/blog/outbound-smtp/gmail-smtp-error-codes-resolve-your-companys-email-delivery-issues/"},"articleSection":"outbound-smtp","keywords":"Security, Updates","wordCount":517,"image":{"@type":"ImageObject","url":"https://media.mailhop.org/duocircle/images/2024/07/phishing-protection-5051.jpg","caption":"SMTP error codes to fix email delivery","width":900,"height":600},"speakable":{"@type":"SpeakableSpecification","cssSelector":[".answer-block","h1"]}} ```