What is a spam trap?

A spam trap is an email address created purely to catch senders who do not maintain their list. Sending to one is immediately expensive.

Pristine traps

Addresses that never belonged to anybody and never signed up anywhere. If you send to one, your list did not come from voluntary sign-ups.

Recycled traps

Formerly real addresses, abandoned for years and reactivated as traps. This is the most common and most treacherous variant: they were legitimate originally.

How you catch them

Bought lists, old lists that were never cleaned, and addresses harvested from the web. Also: typos of well-known domains, which are sometimes monitored.

What it costs

A blocklist entry, which affects all your sending for weeks. There is no quick fix.

How to avoid them

Confirmed sign-up, removal of long-inactive addresses, and never buying a list. Cleaning is the only real prevention.