I maintain a small fee tool for creating API endpoints to trigger email alerts for yourself (varmail.me). Since it's very basic and has no marketing, it doesn't get too many users. You have to click a link in an email to even log in, but I still get bots stuffing my login form with known bad email addresses (I've googled and some of them appear in honeypot lists). There is no chance they can get in, but this is bad because my login verification emails look like spam, since a large percentage of them are sent in response to these bots. So I definitely see some value in a way to pre-screen the emails there.