How to Resolve Outlook SMTP Authentication Errors in n8n Cloud

Below is a summary of steps and troubleshooting tips based on the official Outlook.com Send Email credentials documentation for n8n:

Key Points

• SSL/TLS Toggle:
  The documentation instructs you to turn on the SSL/TLS toggle when using the Outlook.com SMTP settings. In your configuration, you mentioned disabling SSL/TLS with STARTTLS enabled, which is not aligned with the recommended settings. Using SSL/TLS (and not just STARTTLS) is required for secure communication.

• Host & Port:
  The recommended settings are:
  • Host: smtp-mail.outlook.com
  • Port: 587
  Ensure you are using these values, as they are designed for Outlook SMTP.

• App Password:
  Since you have activated Two-Step Verification on your Outlook account, you must use your generated App Password (which you are already using). Just double-check that the App Password is entered correctly.

Troubleshooting the Error

The error message you’re encountering—

Invalid login: 535 5.7.139 Authentication unsuccessful, basic authentication is disabled.

—indicates that Microsoft has disabled basic authentication for your account. Here are a few suggestions:

1. Enable SSL/TLS:
   Reconfigure your SMTP credential in n8n to turn ON the SSL/TLS toggle. This is the setting recommended in the documentation rather than relying solely on STARTTLS.

2. Review Microsoft Settings:
   The error may also mean that your account has been set to require Modern Authentication instead of basic authentication (which is what SMTP in n8n uses). In such cases, check with your Microsoft 365 administrator or refer to Microsoft’s guidance to see if modern (OAuth2) authentication can be enabled or if SMTP basic auth can be re-enabled for your account temporarily.

3. Confirm Server Details:
   Stick with the recommended server details:

   • Host: smtp-mail.outlook.com
   • Port: 587
   • SSL/TLS: Enabled

4. Alternative Approaches:
   If basic authentication can’t be re-enabled and modern authentication is required by your organization or Microsoft, you might need to consider alternative approaches such as:

   • Using a different email provider that still supports basic authentication for SMTP.
   • Setting up an SMTP relay that supports modern authentication (if available).

Next Steps

Double-check your SMTP configuration in n8n with these recommended settings:

PLAINTEXTCopied
User: Your Outlook email address
Password: Your Outlook App Password
Host: smtp-mail.outlook.com
Port: 587
SSL/TLS: Enabled

After updating these settings, try testing the connection again. If you still encounter the basic authentication error, it’s likely that Microsoft’s recent changes (or your organization’s policies) require use of Modern Authentication. In that case, you’ll need to work with your Microsoft 365 or Outlook administrator to determine the best route for SMTP access.

I hope these suggestions help you resolve the issue. Please update your settings accordingly and let us know if you need further assistance!