Verification email failures

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1

Hi,

Recently we have noticed verification email failures on signup AND when triggered manually. Several users who have recently signed up have complained recently. They are not receiving the verification emails and are unable to onboard onto the platform - unless an admin manually sets the verification status to Verified.

I am an admin in our auth0 account and I just tested with my own email I just signed up with. Here is what I see in the logs -

{
“date”: “2025-09-04T14:33:04.868Z”,
“type”: “fn”,
“description”: “To: <>..@gmail.com”,
“connection”: “Username-Password-Authentication”,
“connection_id”: “”,
…
“ip”: “2600:1700:100:6f20:106:5930:2aae:34a7”,
“details”: {
“email_type”: “verify_email”,
….
“error”: “Error sending email: Invalid login: 535 Authorization failed: Authenticated user is not authorized to send mail”
},
….
}

I don’t understand the error details. Whether I trigger the email myself as an admin by clicking ‘Send verification email’ for my gmail user OR on signup - the error is the same.

Any help would be appreciated.

3

Hi @saad2,

Welcome back to the Auth0 Community!

This issue occurs on the custom email provider’s end and means that the email provider is blocking the permission of an authenticated user or application to send emails. If you are using something like Sendgrid for your External SMTP Provider you can trying updating the API keys by enabling Full Access to the assigned permissions.

You can check out this article on the matter - Sending Email Fails with Error “Authenticated user is not authorized to send mail” and can look through the API key permissions information from Sengrid side as well.

I hope this helps your case, and if you have further questions please let me know!

Kind regards,

Remus