Microsoft senders can't send — "client secret expired" (AADSTS7000222)

Symptoms

- Sending (and often syncing) fails for all Microsoft accounts under a single application.
- Customer reports "can't send through Microsoft senders."

Cause
The client secret on the customer's Azure AD app registration has expired. Azure client secrets have a maximum lifetime (Microsoft caps new secrets at 24 months), after which Microsoft refuses to issue access tokens. Without a valid token, Nylas cannot authenticate to Microsoft Graph, so sends and syncs fail. This is a customer-side credential issue, not a Nylas outage — and it affects the whole application, not one grant.

Resolution (customer action)​
1. Sign in to the Azure portal → App registrations → select the affected application.
2. Go to Certificates & secrets → New client secret.
3. Create a new secret (set a long expiry; add a reminder to rotate before it lapses).
4. Copy the new secret Value (not the Secret ID).
5. Update the secret on the Microsoft connector in the Nylas Dashboard (Connectors → Microsoft → credentials).

Update the secret in Nylas Dashboard

1. Log into your Nylas Dashboard

2. Select your application

3.Navigate to App Settings > Authentications (or Connectors)

4.Find your Microsoft connector and click to edit

5.Paste the new client secret Value into the Client Secret field

6.Save changes

Once updated, sending/syncing recovers automatically — no need to reconnect individual accounts.

Common Mistakes

• Copying Secret ID instead of Value: When creating a new secret in Azure, you'll see both a Secret ID (a GUID) and a Value (the actual secret string). You must copy the Value field.
• Not copying immediately: Azure only displays the secret Value once. If you navigate away, you'll need to generate a new secret.
• Looking at expired secrets: Make sure you're copying the Value from the newly created secret, not an old expired one.

References
- Microsoft error code reference (AADSTS7000222): https://learn.microsoft.com/en-us/entra/identity-platform/reference-error-codes

- Nylas auth / connector docs: https://developer.nylas.com/docs/v3/auth/

- How to Renew Microsoft Azure Client Secret for Your Nylas Application

Updated August 04, 2026 14:53