### [Error: InvalidAuthenticationToken: Token Expired](https://wpmailsmtp.com/docs/outlook-invalid-authentication-token/)

**Published:** June 1, 2026
**Author:** David Ozokoye

**Content:**

**Note**: This guide applies to the [Microsoft 365 / Outlook mailer](https://wpmailsmtp.com/docs/how-to-set-up-the-outlook-mailer-in-wp-mail-smtp/ "Microsoft 365 / Outlook") in WP Mail SMTP.

## What This Error Means

The OAuth access token WP Mail SMTP uses to authenticate with Microsoft has expired or been revoked. Microsoft tokens expire and require periodic re-authorization.

## Common Causes

- OAuth refresh token expired after 90 days of inactivity (the token self-renews on each use within that window)
- You changed the Microsoft account password
- An admin revoked app permissions in Azure AD
- Someone modified the Azure app registration after Microsoft issued the token

## How to Fix

Here is the complete step-by-step guide to resolving the error.

### Step 1: Remove the Existing Connection

Start by logging in to your WordPress admin area and going to **WP Mail SMTP » Settings**.

![WP Mail SMTP settings page](https://wpmailsmtp.com/wp-content/uploads/2024/12/general-tab.png)Then, scroll to the **365 / Outlook** section and click **Remove Connection**.

![Remove Connection button in the 365 / Outlook section](https://wpmailsmtp.com/wp-content/uploads/2022/11/remove-connection.png)### Step 2: Re-authorize the Plugin

Start by clicking **Save Settings** to confirm the disconnection. Then, click **Allow plugin to send emails using your Microsoft account**.

![Allow plugin to send emails using your Microsoft account](https://wpmailsmtp.com/wp-content/uploads/2022/12/allow-plugin-to-access-your-account.png)Next, sign in with your Microsoft account in the popup that appears, and click **Yes** to grant the requested permissions.

![Microsoft consent popup](https://wpmailsmtp.com/wp-content/uploads/2022/04/microsoft-consent-popup.png)Finally, wait for the popup to close. Look for the success notification confirming the connection.

![Successfully linked Microsoft account](https://wpmailsmtp.com/wp-content/uploads/2022/12/successfully-linked-microsoft-account.png)### Step 3: Send a Test Email

Confirm the fix by sending a test email.

To test the fix, go to **WP Mail SMTP » Tools** and click the **Email Test** tab. Enter a recipient email in the **Send To** field, then click **Send Email**.

![Test email tab](https://wpmailsmtp.com/wp-content/uploads/2024/10/test-email-tab-1024x1002.png)Once done, check for a success message, then check your inbox to confirm the email arrived.

## Notes

- If this error comes back frequently, check whether you recently changed your Microsoft account password. Password changes invalidate all existing OAuth tokens.
- Security events like a suspicious login can prompt Microsoft to revoke tokens immediately.

That’s It! You now know how to fix the ‘InvalidAuthenticationToken: Token Expired’ error in Microsoft 365 / Outlook and get your emails sending again through WP Mail SMTP.

**Categories:** Outlook Errors, Error Library

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