- This is Microsoft.
- He returns Webhook success with a code 200 and plaintext 1.
- He returns Webhook failure with a code 200 and a string tells its endpoint returned error 400.
- the string didn't tell what exactly the error.
- Don’t be like Microsoft.
EDIT: Got a few details wrong since this happens a few months ago and this meme used to be on r/ProgrammerHumor. Also the proof: 
Wait, do you know if this still happens?
I have a ticket in our backlog to investigate similar issue with Teams Webhook reporting success but not posting anything.
None of us wanted to look at it so been in our backlog for a whilr
Yep, this still happens
There's a video somewhere by someone... Returning a blank document instead of an error code is sometimes a QoS decision. Clients won't make a new request without the user intervention, so whatever resource that's bottlenecked has time to catch up
Since it's been months, I haven't checked... Will possibly take a look later