Types of spam traps
Pristine traps are addresses that were never used to sign up for anything and only exist to catch senders who buy or scrape lists — there is no legitimate way to have acquired one. Recycled traps are former real mailboxes that were abandoned, then reactivated by the provider specifically to catch senders with stale, unverified lists.
How spam traps end up on your list
Purchased or scraped lists are the most common source of pristine traps. Recycled traps can also end up on a legitimate, organically-built list if you never re-verify: an address that was real and opted-in years ago may have since been abandoned by its owner and reactivated as a trap by the mailbox provider.
How to avoid spam traps
Never buy or scrape email lists. Use double opt-in for sign-ups. Verify every address before sending, and re-verify regularly — a spam trap that was a real address when you first collected it can quietly become a trap months later without any action on your part.
Spam traps vs. inactive subscribers
Not every unresponsive address is a trap. An inactive subscriber who simply stopped opening emails is a re-engagement problem, not a reputation risk — the key distinguishing signal is whether the mailbox itself still exists and accepts mail (which verification can confirm) versus whether the owner is actively reading (which verification cannot confirm). Traps are specifically addresses the mailbox provider controls, not just addresses that happen to be quiet.