We just noticed that the incoming webhooks feature broke sometime around 07/23 12:50am UTC. The webhook returns with HTTP 200 OK, and the only error message is a .NET exception message without the stack trace. Is there a schema change recently that is being rolled out?
Oddly, this only affected half of our configured webhooks. Newly created webhooks function normally.
$ httpie --json -v POST $url 'text=This is a test.' POST <redacted> HTTP/1.1 Accept: application/json, */* Accept-Encoding: gzip, deflate Connection: keep-alive Content-Length: 111 Content-Type: application/json Host: outlook.office.com User-Agent: HTTPie/1.0.2
@Ines_Trenz_HIRSCHTEC After digging around it looks like Incoming Webhook (and all apps) are added to the account level O365 blacklist. I logged into the Office admin -> Admin Centers -> Teams -> Teams Apps -> Permission Policies -> Org-wide app settings -> Blocked apps, and click X on the Incoming Webhook. After this I needed to wait ~2-4 hours. It seemed that some channel webhook's were quicker to come back than others.