Spam trap

A spam trap is an address a mailbox provider or blocklist operator monitors specifically to identify senders with poor list practice. Nobody signs up with it, so any mail arriving at it got there by a route that did not involve consent.

There are two kinds and they say different things about you. A pristine trap was never a real address: it was published somewhere a scraper would find it and nowhere a person would ever type it, so mail to it means the address was harvested or bought. A recycled trap was once a real mailbox that its owner abandoned; the provider let it hard-bounce for a period and then reactivated it as a trap. Mail to it means the list has not been cleaned in a long time.

Hitting either can affect delivery for everything else you send, which is what makes them disproportionate to their number. A single pristine trap can be enough to get a sending domain listed.

Verification does not identify traps, and cannot. A trap is indistinguishable from a working mailbox at the protocol level — that is the entire design of it. What verification does is remove the conditions traps live in. Recycled traps are old addresses that stopped working before they were reactivated, so a list checked regularly loses them while they are still bouncing. Pristine traps arrive with purchased or scraped data, which is a sourcing problem rather than a verification one: the check that prevents those is the one at the point of collection.