[mst]

Right, but in this case - as confirmed by Heroku when contacted - something went wrong at their end and the emails weren't sent in the first place.

The fact that the failure to send a single warning email to this particular customer wasn't both detected and considered a five alarm fire level bug under the circumstances is the thing that moved the decision to sunset the free tier from sad to disastrous for the user who posted the Tell HN in the first place.