Why does clicking "Authorize" on my SMTP OAuth2 connector return an immediate error?

Environment / Context

Applies to any KnowledgeOwl account using SMTP with OAuth2 (Microsoft/Azure). The Authorize button returns an immediate error rather than completing the authorization flow.

Resolution

The Azure app registration secret has likely expired. Create a new one and update your KnowledgeOwl SMTP settings.

1. In Azure, navigate to your app registration.
2. Go to Certificates & secrets and create a new client secret. Set the expiration to 1 year or longer (the default is 6 months).
3. Copy the new secret value and update it in your KnowledgeOwl SMTP connector settings.
4. Click Authorize again. The error should be resolved.
5. Send a test email to confirm everything is working.

Cause / Background

Azure client secrets have a default expiration of 6 months. Once expired, the OAuth authorization flow fails immediately. If your SMTP connector was working previously and stopped without any other changes, an expired secret is the most likely cause.

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