Catch-all email
A catch-all (or accept-all) email domain is configured to accept mail sent to any address at the domain, even non-existent mailboxes, rather than rejecting unknown recipients. This makes it impossible for a verifier to confirm whether a specific address truly exists.
How it works
The server returns 'accepted' for every recipient at the domain. A verifier therefore can't distinguish a real mailbox from a typo, so it classifies the address as catch-all / risky rather than valid.
Why it matters
Catch-all addresses can still bounce after acceptance, and a list heavy with them inflates apparent deliverability while quietly raising real bounce risk. They need a sending strategy, not blind trust.
How can you tell whether a domain is set to catch-all?
Ask the server about an address that cannot exist. A verifier checks the real address and also a random string at the same domain, something like [email protected]. If the server accepts the nonsense address too, it accepts everything, and its acceptance of the real one tells you nothing. That is the test behind the catch-all label in a verification report.
The label can change. A company may switch mail systems, add or remove a security gateway, or configure catch-all only for a period during a migration, so a result from months ago may no longer hold. Recheck catch-all domains before each large send rather than carrying the old label forward.
How should you size a first send to catch-all addresses?
Start with a slice and wait long enough to see late bounces, because catch-all servers often accept the message and reject it afterwards with a separate bounce notice. In a hypothetical segment of 800 catch-all addresses, send to 100 and wait 48 hours. If 6 bounce, that is 6% and the rest of the segment needs more evidence before it is mailed. If 1 bounces, continue in batches of 100 a day while watching each batch.
Keep these sends on mailboxes that are not carrying your main campaigns, so a poor result dents a small part of the program. The catch-all deliverability guide covers segment rules in more depth. Record the results by domain as well, since a domain that produced late bounces once is likely to do so again.
Which signals raise confidence in a catch-all address?
Evidence from outside the mail server. If other people at the same company replied to addresses in the same first.last pattern, the pattern is probably right. A current profile on LinkedIn showing the person still works there rules out the most common failure, a departed employee. An address published by the person on the company website is stronger still.
When the email address stays uncertain, the contact can still be reached. A sequence that opens with a LinkedIn step or a call and sends email later, once the person has engaged, avoids betting a mailbox's standing on an unconfirmed address.
Why do companies configure their domain to accept all mail?
Security gateways are the case most likely to mislead a verifier. The gateway answers the RCPT TO question on behalf of the real mail server behind it, says yes to everything, and only passes the message inward once its own scanning is done. The mailbox may exist or not; the gateway will not say. From the sender's side that looks identical to a domain deliberately set to accept all mail.
Usually to avoid losing mail. Catch-all routing sends misspelled addresses and mail for departed staff to a shared inbox, and some security gateways accept every message first and filter afterwards. The consequence for a sender is that mail to a former employee may reach someone else or be discarded without any notice. Autocloz flags catch-all and risky results during email verification so they can be segmented instead of mixed into validated sends, and any that fail later are handled as a hard bounce.
How Autocloz handles it
Autocloz flags catch-all and risky addresses during verification so you can segment them, send conservatively, and watch their bounce behaviour rather than treating them as fully validated.
Free tools for this
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FAQ
Should I email catch-all addresses?
Cautiously. Isolate them into a separate, low-volume segment, monitor bounces closely, and remove any that bounce. Don't mix unverified catch-alls into your main warmed sending.
Related terms
Mailbox warmup is the practice of gradually increasing a new email account's sending volume while generating positive engagement (opens, replies, moving mail out of spam) so mailbox providers build trust in the sender before real campaigns ramp up.
Sender reputation is the trust score mailbox providers assign to your sending domain and IP based on how recipients react to your mail — opens, replies, spam complaints, bounces and spam-trap hits. A high reputation lands you in the inbox; a low one routes you to spam or blocks you.
Email bounce rate is the percentage of sent emails that are returned undelivered. Hard bounces are permanent (invalid or non-existent address); soft bounces are temporary (full mailbox, server down). A high bounce rate signals a poor list and damages sender reputation.
A spam trap is an email address operated by mailbox providers and blocklist operators specifically to catch senders with poor list hygiene. There's no real person behind it, so any mail it receives indicates you're emailing addresses you didn't earn permission to contact.
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