This article addresses an issue where an "Unsubscribe" link or button appears in emails sent from Auth0, even when this link is not included in the configured email templates. This can affect various transactional emails, such as Welcome, Password Reset, and Verification emails.

• Email Templates
• Custom SMTP Provider

Auth0 does not automatically add an unsubscribe link to emails if it is not explicitly part of the email template's HTML code. The appearance of this link is typically caused by external factors:

1. Custom SMTP Provider: Many external email service providers (ESPs) have a feature that automatically injects an unsubscribe footer or link into outgoing emails. This is often a default setting to help with email deliverability and compliance with anti-spam laws (e.g., CAN-SPAM).
2. Recipient's Email Client: Some email clients, such as Gmail or Outlook, may automatically detect emails that appear to be from a mailing list and generate their own "Unsubscribe" link in the email header for the recipient's convenience. This behavior is controlled by the email client and not by Auth0 or the email provider, and this is not something that can be disabled by the sender.

The solution is to investigate and disable the automatic unsubscribe link feature within the configured custom SMTP provider's settings.

If after confirming the settings in the custom SMTP provider the link still appears for some users, it is likely being generated by the recipient's email client and is outside the control of Auth0 or the SMTP provider.