To combat phishing, Gmail now requires bulk senders (over 5,000 emails/day) to undergo a verified badge process similar to X/Twitter. This means temp mail services, which often relay unauthenticated mail, are increasingly unable to reach Gmail inboxes.
To make it truly "temp," Leo didn't want to see these emails at all. He set up a simple Gmail Filter Any email sent to *+temp@gmail.com "Skip the Inbox" and "Apply Label: Burner." The Secret Sauce: gmail temp mail updated