Expected Behavior of Existing webhook.office.com/webhookb2 Endpoints After Office 365 Connector Retirement

Hi @Angelo

Based on the currently available Microsoft documentation, Office 365 Connectors in Microsoft Teams were scheduled to be progressively disabled from May 18, 2026 through May 22, 2026. Microsoft states that after this rollout, Office 365 Connectors will no longer function and that all connector-based webhooks must be migrated to Power Automate-based Workflows before the rollout begins.

However, I could not find an official Microsoft document that defines the exact HTTP-level behavior for existing *.webhook.office.com/webhookb2/... endpoints after retirement. Specifically, the documentation does not appear to guarantee a specific status code such as 403, 404, or 410, nor does it document an automatic redirect to another service.

For monitoring and operational planning, it would be safest not to rely on a particular HTTP response code from the retired endpoint. Instead, treat the legacy webhook endpoint as unsupported after the retirement rollout and validate migration based on successful delivery through the new Workflows webhook endpoint, including end-to-end confirmation that messages are posted to the intended Teams channel.

If your organization requires an official HTTP failure-mode guarantee for compliance or monitoring design, I would recommend opening a Microsoft support request or documentation feedback item, because the currently published retirement and Teams webhook documentation confirms the retirement but does not specify a stable post-retirement HTTP response contract.

Ref: Manage Microsoft 365 connectors and custom connectors
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Thank you.

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