Catch-All Server Detector
Check if a domain's mail server accepts email for any address, making individual mailbox verification unreliable.
What is a Catch-All Server?
A catch-all (or accept-all) mail server is configured to accept email sent to any address at its domain, regardless of whether that specific mailbox actually exists. For example, if company.com has a catch-all configuration, emails sent to [email protected], [email protected], or any other address would all be accepted.
Catch-all configurations are common in small businesses and organizations that want to ensure they never miss an email, even if it's addressed to a misspelled name or a former employee. The server accepts everything and typically routes unmatched addresses to a general inbox or administrator.
Our detector works by testing whether the mail server accepts a randomly generated, clearly non-existent address at the domain. If the server accepts it, the domain is flagged as catch-all.
Why Does Catch-All Detection Matter?
Catch-all detection is crucial because it directly affects the reliability of SMTP verification. When a server accepts all addresses, a positive SMTP verification result doesn't confirm that the specific mailbox exists — it only confirms the server is configured to accept everything.
For email list quality, catch-all domains represent a grey area. The email might be valid, or it might bounce later when the catch-all server can't route it internally. Many email marketers treat catch-all addresses as "risky" and segment them separately, sending to them with extra caution and monitoring bounce rates closely.
Frequently Asked Questions
Should I remove catch-all emails from my list?
Not necessarily. Many valid emails exist on catch-all servers. Instead, segment them as "risky" and monitor bounce rates when sending to them. If you see high bounce rates from a catch-all domain, consider removing those addresses. Our full validator gives catch-all addresses a lower confidence score to reflect this uncertainty.
How common are catch-all servers?
Roughly 10-20% of business domains use catch-all configurations. They're more common among small businesses and less common among large enterprises that have standardized email management. Free email providers like Gmail never use catch-all configurations.
Can catch-all detection be wrong?
Rarely, but possible. Some servers implement greylisting (temporarily rejecting unknown senders) or rate limiting that can interfere with the test. Additionally, a few servers accept all RCPT TO commands during the SMTP handshake but bounce the email later during delivery — this is called "deferred rejection."