Deliverability
Spam trap
An email address with no real owner, used by mailbox providers and blocklists to catch senders with poor list hygiene — sending to one is a strong negative signal.
Types of spam traps
- Pristine traps: addresses that were never used by a person and never signed up for anything. Hitting one usually means a scraped or bought list.
- Recycled traps: abandoned addresses that a provider has repurposed after a long period of bounces. Hitting one means you kept mailing an address long after it died.
- Typo traps: addresses on misspelled domains, such as gmial.com, caught when signups aren’t validated.
Why they’re so damaging
A spam trap never opens, clicks or complains. It just records that you sent to it. Because no legitimate sender should ever reach one, a hit is one of the strongest signals that your list-building is broken, and can lead straight to a blocklist listing.
How to avoid them
Never buy or scrape lists. Validate addresses at signup, suppress hard bounces immediately, and stop mailing contacts who haven’t engaged in a long time. MailCraft’s email validation catches malformed addresses, domains without mail servers, and disposable domains before they reach your list.
Let MailCraft handle the details
Authentication, bounces, complaints and suppression are built in. Start free with 3,000 emails a month, no credit card required.
Start freeRelated terms
Full glossaryDeliverability
Blocklist (or blacklist)
A list of IPs or domains flagged as sources of spam or abuse, checked by many receiving servers before accepting mail — landing on one can tank deliverability until you’re delisted.
Sending & delivery events
Hard bounce
A permanent delivery failure — the address or domain doesn’t exist. Hard bounces should be suppressed immediately and never retried.
Email types & metrics
Double opt-in
A signup flow that requires a subscriber to confirm their email address via a confirmation link before they’re added to a marketing list.