Incoming webhook to Microsoft Teams intermittently fails with 403 errors

Hi Machado Danette

Thank you for reaching out to Microsoft Q&A forum

Based on your description, I understand that you are intermittently receiving HTTP 403 errors when posting to a Microsoft Teams channel using an Incoming Webhook, even though the webhook URL is valid and the MessageCard payload and headers have not changed.

As far as I know, the intermittent 403 responses from Microsoft Teams Incoming Webhooks commonly occur due to backend behaviors in the Teams connector service, where certain tenants or channels temporarily reject webhook submissions despite valid request formatting. This can also happen when webhook requests exceed hidden rate limits (more than four requests per second) or when message size approaches the 28 KB limit.

In this context, based on my knowledge, you can try the below approaches:

Validate basic limits and stabilize request patterns

• Ensure payload size stays under the 28 KB MessageCard limit.
• Keep requests below 4 per second for each webhook.
• Implement retry logic with exponential backoff

Verify webhook configuration and permissions

Confirm that the Incoming Webhook connector is still active on the channel and that no tenant policies have disabled or restricted its use. If needed, generate a new webhook URL and test the same payload to rule out a corrupted or invalidated endpoint.

Link references:

https://learn.microsoft.com/en-us/microsoftteams/platform/webhooks-and-connectors/how-to/connectors-using?tabs=cURL%2Ctext1#rate-limiting-for-connectors

https://learn.microsoft.com/en-us/microsoftteams/limits-specifications-teams#teams-and-channels

https://learn.microsoft.com/en-us/microsoftteams/platform/bots/how-to/rate-limit

Hope my answer will help you.

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