Fix the ‘550-5.7.26 This mail is unauthenticated.’ Gmail error
Definitions
The ‘550-5.7.26 This mail is unauthenticated‘ Gmail error means your email was rejected because it wasn’t properly verified with SPF or DKIM, which Gmail (Google) requires for all senders.
In short, Google won’t let you send emails to Google-based email addresses until you authenticate your domain name with SPF or DKIM.
The error can also appear as ‘Your email has been blocked because the sender is unauthenticated.‘
Here is an example of what the error message looks like:
Before you start
🚨 This error is caused by Google authentication requirements and is unrelated to your email service.
⚠️ Do not resend your email until after you’ve authenticated your domain via SPF, DKIM, or both.
Step by step
You can activate either SPF or DKIM domain authentication, as Gmail only requires one active authentication method to accept your emails. If you’d like to activate both, you can as well.
SPF
SPF. Activate SPF on the domain name associated with your email address
🤔 What is SPF?
SPF (Sender Policy Framework) is an email authentication system that uses DNS to check if a mail server is authorized to send emails from your domain name.
⁉️ How can I check
✅ If your domain name uses our nameservers, SPF is activated automatically. No action is required by you.
⚠️ If your domain name uses external DNS, a CDN provider (Cloudflare, etc.), or an external email service, you have to activate SPF yourself. Go to this guide for steps: Manage your SPF record
DKIM
DKIM. Activate DKIM on the domain name associated with your email address
🤔 What is DKIM?
DKIM (DomainKeys Identified Mail) is a system to authenticate your email, ensuring it genuinely came from your domain and that email truly originates from you.
⁉️ How can I check
✅ If your domain name uses our nameservers, DKIM is activated automatically. No action is required by you.
⚠️ If your domain name uses external DNS, a CDN provider (Cloudflare, etc.), or an external email service, you have to activate DKIM yourself. Go to this guide for steps: Manage your DKIM record