One-Time Password (OTP) verification emails fail to send when a Passwordless Connection uses Azure Communication Services. This issue occurs because Azure Communication Services requires a raw email address in the sender field, while the default Auth0 configuration uses a formatted string. To resolve this, modify the default sender address in the Passwordless settings to a raw email address format.

System logs during the login process when the setup is misconfigured:

• Successful “Code/Link Sent” log
• “Failed Sending Notification” log with the error: “Error sending email: Request body validation error. See property ‘senderAddress’”

• Passwordless Connections
• Azure Communication Services
• Email Verification

Azure Communication Services only supports a raw email address (e.g., <user@example.com>) in the From field. The default Auth0 Passwordless configuration uses a formatted string, {{ application.name }} <root@auth0.com>, which causes the email delivery to fail when routed through Azure

To resolve the email delivery failure, navigate to the Auth0 Dashboard and update the sender address in the Passwordless email settings to a raw email format.

1. Navigate to the Auth0 Dashboard.
2. Go to Authentication and select Passwordless.
3. Choose the Email connection.
4. Locate the From field.
5. Change the default value ({{ application.name }} <root@auth0.com>) to a raw email address (for example, <user@example.com>).
6. Save the changes.

Related References

• Configure Azure Communication Services as an Email Provider