---
title: Invalid base scope for reference OAuth 2 Application (Outlook)
description: "Invalid base scope for reference OAuth 2 Application Error\nHow to fix Outlook's Invalid base scope for reference OAuth 2 Application Error"
---

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# Invalid base scope for reference OAuth 2 Application (Outlook)

## Invalid base scope for reference OAuth 2 Application Error How to fix Outlook's Invalid base scope for reference OAuth 2 Application Error

If your messages aren’t sending and you encounter the error **“Invalid base scope for reference OAuth 2 Application Error,”** this usually means that SMTP AUTH is not enabled on your Outlook account.

Once you turn on SMTP AUTH, the authentication process will work correctly, and your messages should go through without any problems.

![](https://help.startups.com/hs-fs/hubfs/image-png-Dec-04-2025-04-32-10-6014-PM.png?width=670&height=202&name=image-png-Dec-04-2025-04-32-10-6014-PM.png)

Check instructions on how to enable SMTP AUTH in your account here: [**https://learn.microsoft.com/en-us/exchange/clients-and-mobile-in-exchange-online/authenticated-client-smtp-submission#enable-smtp-auth-for-specific-mailboxes**](https://learn.microsoft.com/en-us/exchange/clients-and-mobile-in-exchange-online/authenticated-client-smtp-submission#enable-smtp-auth-for-specific-mailboxes)

**![](https://help.startups.com/hs-fs/hubfs/image-png-Dec-04-2025-04-41-24-3924-PM.png?width=670&height=328&name=image-png-Dec-04-2025-04-41-24-3924-PM.png)**

Once done, please "**Authorize Access with Microsoft**" one more time and choose "**Outlook IMAP/SMTP**" option.  The final step is to perform a delivery test to confirm connection.

---

Note that you’ll need admin access to complete this. If you don’t have it, please reach out to your admin for assistance with the setup.

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