> But the worst Digital Ocean incident we ever had was when they turned all our droplets off all at once. The credit card entered into the account had expired, there was no backup card, and the contact email on the account went to a shared inbox that was not monitored. So for probably a month we were getting and ignoring billing alerts, until we really paid attention when everything was offline and not responding to…
I'd say that your service is dead unless proven otherwise. Your bills are unpaid unless proven otherwise. I'd be alerted by absence of regular emails telling me that my card was billed for the hosting service.
I'd say you're dead right -- this is the only safe assumption. And any email client smart enough to check incoming email against a regexp could be extended to raise a not-easily-ignored alert if no pattern match (indicating success in processing a payment) had arrived by some chosen date of the month. Yet I've never come across such a feature in Gmail, Fastmail, nor Thunderbird. Maybe someone sometime has hacked such a thing into Gnus ...