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✉️ Email Delivery

Documentation, reference material and tutorials for CRM-NG SMTP Email: setup guides for every mail service, troubleshooting, and one article per error message.

Error: 400 invalid_request (Microsoft 365)

Updated

By Duane GarnerChief Executive Officer (CEO)
Summarize: Claude ChatGPT View Markdown
On this page

Microsoft refused the token request because a value in it is missing or wrong, usually the Tenant ID or the Application (Client) ID.

This article is for sites using the 365 / Outlook mailer where sending fails because Microsoft answered the token request with HTTP 400 and invalid_request.

The error as you see it

Microsoft 365 token request failed: invalid_request (often followed by a code such as AADSTS90002, AADSTS900023 or AADSTS900144 and a short reason)

Shown by the 365 / Outlook mailer, in the failed-send banner, in Tools → Debug Events and in the Email Log.

What this error means

The plugin signs in to Microsoft Entra ID with the app's credentials to get an access token, then uses the token to send through Microsoft Graph. invalid_request with status 400 means Microsoft could not process the sign-in request at all, because something in it is missing or does not make sense. No email was attempted. The AADSTS code after it tells you which value is at fault:

Code What it points to
AADSTS90002 The tenant in Tenant ID does not exist.
AADSTS900023 Tenant ID is neither a valid ID nor a valid domain.
AADSTS900144 A required value, usually the client ID, is empty.

Common causes

  • A typo in Tenant ID, or a value copied from the wrong field (for example the Object ID or the subscription ID).
  • A domain in Tenant ID that is not part of your tenant, or that was removed from it.
  • An empty or mistyped Application (Client) ID, sometimes with a stray space or line break from copying.
  • Constants in wp-config.php that override the settings page with outdated values.

How to fix

  1. Read the full code

    Open CRM-NG SMTP → Tools → Debug Events and find the newest Email Sending Errors entry. Note the AADSTS code.

  2. Open your app registration

    Go to https://entra.microsoft.com/, then Identity → Applications → App registrations, and open the app you made for this site.

  3. Copy the IDs

    On Overview, copy Directory (tenant) ID and Application (client) ID. Use the copy buttons beside them rather than selecting the text by hand.

  4. Check the secret too

    Under Certificates & secrets, make sure the secret you use is listed and not expired. If you are unsure, create a new client secret and copy its Value (not the Secret ID) straight away.

  5. Update CRM-NG SMTP

    In CRM-NG SMTP → Settings → General, with 365 / Outlook selected, paste Tenant ID and Application (Client) ID. If you made a new secret, use Remove Client Secret and paste the new value into Client Secret. Press Save Settings.

  6. Check for constants

    If a field cannot be edited, it is set by a CRMNG_SMTP_* constant in wp-config.php. Correct it there.

  7. Send a test

    Go to CRM-NG SMTP → Tools → Email Test, fill in Send To and press Send Email.

Verify it worked

The test page shows "Test email sent successfully! Check your inbox to confirm delivery." and a copy sits in the From Email mailbox's Sent Items.

Notes

  • If the error instead says invalid_client, the client secret is wrong or expired. The most common slip is pasting the Secret ID instead of the secret's Value; the plugin's own hint reads "Use the secret Value (not the Secret ID)."
  • AADSTS50194 has its own article: AADSTS50194: single-tenant application.
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