My Alert Pipeline Dropped Three Weeks of "Unknown" Emails Because a Webhook 403'd

I run a small Python script that polls an IMAP inbox every fifteen minutes and triages new mail into three buckets: customer inquiries, Stripe payment notifications, and everything else. Each bucket has its own alert path. For three weeks, the third bucket alerted nothing. I didn't notice until I went looking. Here's what happened, what the bug actually was, and what I replaced it with. If you have any kind of fan-out alerting pipeline, there's probably a version of this waiting in your repo. Th