How to fix the 550-5.7.26 Gmail error?

You might have been sending emails using Gmail for years now, but that’s not a good enough reason for the Email Service Provider (ESP) to let your email in, even if it feels like something’s off. Since email-based attacks are becoming so frequent and rampant, your sender reputation and good faith no longer suffice, given today’s threat landscape. That is why Gmail and other ESPs verify every email they receive before delivering it to the recipient’s inbox. 

Now, while sending emails, if you come across a 550-5.7.26 error, it simply means that Gmail is not able to authenticate your domain properly. This essentially means that Gmail is not convinced that the email is genuinely from you. This error occurs when the three records in your DNS—SPF, DKIM, and DMARC —are not set up properly. 

Because these records act as the identity checks for your domain, any mismatch makes Gmail reject the email to avoid delivering something that could be unsafe.

In this article, we will understand what exactly the 550-5.7.26 Gmail Error is and what you can do to fix it.

What does the 550-5.7.26 Gmail error even mean?

When you see the 550-5.7.26 error, it is basically Gmail telling you that it couldn’t verify the identity of the email you were trying to send.

As you know, every time you send an email, it doesn’t just directly reach the recipient; it goes through a thorough security process on the ESP’s end. So, before Gmail allows your message into someone’s inbox, it checks whether the email is genuinely coming from your domain.

To do this, Gmail looks at three key records, SPF, DKIM, and DMARC, that tell the mail provider whether your domain is authorised to send that email in its own unique way. SPF confirms if the server is authorized to send emails on your behalf. DKIM adds a digital signature that shows the email hasn’t been changed on the way. And DMARC ensures that SPF and DKIM align, and tells Gmail what to do if they don’t.

Now, if any problem with any of these records, whether it’s wrong, missing, or misconfigured, it immediately creates doubt. Gmail can’t be sure the email really came from your domain, so instead of taking a chance, it blocks the message and shows the 550-5.7.26 error.

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Why exactly are you seeing this error message?

We now know that if you are seeing this error message, it means something is not right with your authentication setup. Gmail cannot verify that your email came from your domain, so it blocks the message instead of delivering it. But what causes this to happen in the first place?

Well, the reasons behind this might differ based on your sending practice. Let’s dig deeper and understand them:

You send more than 5000 emails per day

• You have neither implemented SPF nor DKIM for your domain
• Your domain is missing a valid DMARC record
• Your “From:” header looks too similar to Gmail’s own addresses, making it appear spoofed.
• Your emails are not sent through a TLS-secured connection
• ARC (Authenticated Received Chain) is not enabled for forwarded messages.
• There is something wrong with your forward and reverse DNS
• You do not offer recipients an easy way to unsubscribe from your marketing emails.

You send fewer than 5000 emails a day

• Your domain is not authenticated with SPF or DKIM
• Your spam rate is high (above 0.3%)
• Your Gmail “From:” header is being impersonated by someone else
• You are not using a TLS-secured connection
• You do not have ARC enabled for forwarded emails 
• There are errors in your forward and reverse DNS

How can you fix this error?

Now that we know why the 550 5.7.26 This Mail is Unauthenticated error appears, let’s understand how you can fix it:

• Begin by implementing SPF and DKIM for your domain to make sure Gmail can verify who is allowed to send emails on your behalf and confirm that your messages are genuine.
• Next, configure DMARC so that the ESP can confirm your emails pass SPF or DKIM and understand how to treat messages that fail these checks.
• If you send marketing emails, make sure you add a simple unsubscribe button so people can easily stop getting emails they don’t want. Gmail expects this, and it also helps you avoid spam complaints.
• Finally, ensure that your outgoing emails comply with Gmail’s latest sending practices. These requirements are updated regularly, and staying up to date helps your emails reach inboxes smoothly and securely. 

Need help fixing the 550-5.7.26 error? The DuoCircle team is here to help you with it all. Get in touch with us today to properly authenticate your domain and ensure your emails are delivered securely and seamlessly.