Spam trap

Two kinds, two causes

Pristine traps are addresses created only to catch senders, published where only a scraper would find them and never owned by a person. They are also called honey pots. The only way to mail one is to have harvested the address, which tells the mailbox provider exactly how your list was built.

Recycled traps are real addresses that were abandoned. After a mailbox has been dead for a long time, with a long period of bouncing first, a provider can reactivate it as a trap. Hitting one says your list is old and unmaintained, not that it was scraped.

Why they are so costly

Mailbox providers and blocklist operators treat a trap hit as strong evidence, stronger than an ordinary bounce. The consequence is not one failed email but a mark against the sending domain and IP that can send everything to spam, and lift only slowly.

You cannot see them, so you prevent them

A verifier cannot tell you an address is a trap: the server accepts the mail like any other. What you control is the behaviour that leads to traps:

• Do not buy, rent, or scrape lists.
• Remove hard-bounced addresses at once; a bounce is often the stage before recycling.
• Re-verify any list older than a few months before sending.
• Stop sending to addresses with no engagement over a long period.

If you suspect a listing, check the major blacklists, then fix the cause rather than only the symptom.