422 error Microsoft 365

awr10e
(@awr10e)

1 week, 3 days ago
Hi

Just been made aware that a clients emails have stopped working, looking at the logs it started 15 Jul 2026.

I’ve tried relinking the server tokens and get the issue
```
{
  "code": 422,
  "message": "Unauthorized",
  "errors": null
}
```
Tried the disable encryption checkbox and it still fails

Viewing 4 replies - 1 through 4 (of 4 total)

Plugin Support Ariful Islam
(@arifulislam1)

5 days, 7 hours ago
Hi @awr10e ,

Sorry you’re running into this.

The 422 Unauthorized here is usually coming from the Microsoft auth/token validation step, not from the Disable Encryption option. The Outlook / Microsoft 365 connection in FluentSMTP uses Microsoft Graph API, so SMTP encryption settings generally won’t affect this part.

Since the emails stopped on July 15, 2026 and re-authentication is also failing now, the first thing I’d check is the Microsoft app registration:
1. In Microsoft Entra / Azure > App registrations > Certificates & secrets, confirm the client secret is still valid and that you copied the Client Secret Value, not the Secret ID.
2. In Authentication, make sure the Redirect URI exactly matches the callback URL shown in FluentSMTP, for example:
  https://yourdomain.com/wp-json/fluent-smtp/outlook_callback
3. Please confirm you are authenticating with the same Microsoft 365 mailbox that is set as the sender / From email in FluentSMTP.
4. Make sure the app is still enabled and the required Microsoft Graph permissions are granted.
After checking those, please disconnect/reconnect the Microsoft connection, generate a fresh auth code, save it again, and test once more.

If it still returns 422, please share the full Microsoft/AADSTS error you see during the auth step or a screenshot from the browser network response. That will help us tell whether this is a secret expiry, redirect URI mismatch, or tenant permission issue.

Thank you.
Thread Starter awr10e
(@awr10e)

5 days, 4 hours ago

Hi

Everything is setup as per your instructios.

the client secret was still valid for another 12 months, but i created a new client secret, to see if that helped.

I’ve tried reauthenticating but still get 422 when running the test email. There is no error when getting the auth token

What do you mean by Microsoft Graph permissions?

Thread Starter awr10e
(@awr10e)

3 days, 9 hours ago

@arifulislam1

This issue is still not resolved my client is still having problems. How has this being marked as resolved???

Nothing has changed it just stopped working

I’ve resetup everything and it still fails
Plugin Support Ariful Islam
(@arifulislam1)

3 days, 5 hours ago
Hi @awr10e ,

The 422 Unauthorized response with Microsoft 365 usually means the Microsoft app/token is no longer being accepted, even if the connection was working previously. Since your logs show this started around July 15, 2026, I’d recommend checking the Microsoft app configuration first.

Please go through these points:
1. Make sure the email address set as the From Email in FluentSMTP is the same Microsoft 365 account used to authorize the connection.
2. In your Azure/Entra app, confirm the Redirect URI exactly matches the callback URL shown in FluentSMTP.
3. Verify the required Microsoft Graph permissions are still present and admin consent is granted.
4. Confirm the mailbox is active and properly licensed in Microsoft 365.
5. Remove the current Microsoft connection from FluentSMTP, then reconnect it once after verifying the above.
If the issue remains, please share:
- a screenshot of the FluentSMTP Microsoft connection settings
- a screenshot of the Azure/Entra app Authentication and API permissions sections
That will help us narrow it down further. Also, I will mark the topic as not resolved until resolved.

Thank you.

Viewing 4 replies - 1 through 4 (of 4 total)

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