This article explains the cause of the following error that occurs when an attempt to send an email is made:

Authenticated user is not authorized to send mail

The error seen in the logs looks like this:

{
   ...
  "type": "fn",
  ...
  "details": {
   ...
    "error": "Authenticated user is not authorized to send mail"
  },
  ...
}

• External SMTP Provider
• Custom Email Provider
• Email

The error Authenticated user is not authorized to send mail when using Auth0 usually means that the email service provider (like SendGrid, Amazon SES, etc.) is not allowing the authenticated user or the application to send emails on their behalf.

Resolve the error by updating the permissions for the API key generated in your External SMTP Provider / Custom Email Provider.