Overview
This error occurs when the authentication attempt reaches your specified email server, but the server explicitly rejects the credentials or denies access. This means the OAuth 2.0 exchange was technically accepted, but the login was refused for policy, account, or other reasons.
Event example
See an example of the OAuth2 response failed Event message:
- Task "Weekly Invoices" Action "Send Email" error: OAuth2 response failed (535 5.7.3 Authentication unsuccessful [GVX0EPF00014ADE.SWEP280.PROD.OUTLOOK.COM 2025-03-19T12:57:23.008Z 08DD4C2AC2FC4950]).
Cause
Common causes of this issue include:
- Incorrect or expired OAuth tokens.
- The required API scopes are missing or incorrect.
- The app was not granted permission or was revoked by the user or administrator.
Solution
Ensure that OAuth and App scopes are typed correctly and necessary permissions are granted by the user and/or administrator.
Renew your OAuth 2.0 credentials if they've expired or been revoked. For the user consent flow, click the Sign-in button to generate new OAuth tokens. For the service flow, follow the procedures specified by your email provider.
Questions?
If you have any questions, please do not hesitate to contact our support team.