- Accept-all, defined
- Accept-all is the server behavior behind a catch-all domain: the mail host answers 250 to every recipient it is offered, including addresses that were invented a second ago.
The name describes what the server does rather than how it was configured. Some hosts genuinely route every address to one inbox. Others reject unknown users later, at delivery, after the handshake has already ended.
You find out by probing. Offer the server a local part like q7x4zz-nobody at that domain and watch what it says. A 250 there tells you the 250 you got for your real address carried no information.
This matters because the two answers are byte-identical. A verifier that skips the probe will report both as valid, and you only learn the difference when the campaign bounces.
Accept-all is a property of the receiving host on the day you asked. A domain can stop behaving this way after an admin changes the recipient policy, so a six-month-old result is worth re-running.
How ZapBounce reports it
Every domain gets the random-address probe before we score your address. If the server accepts the invented recipient, your result comes back catch_all with the reason accept_all_domain, so you can see it was the probe that made the mailbox unprovable. That result costs a credit like any other, since the finding about the domain is real.
The same 250, twice, by hand
You can watch this happen from any machine with port 25 open. Connect to the domain's mail host, greet it, give a sender, then ask about a colleague you know works there: RCPT TO:<maria.lopez@example.com>. The reply is 250 2.1.5 OK. Now ask about RCPT TO:<zq81-nobody-here@example.com>, and the reply is 250 2.1.5 OK again, character for character.
That second answer is the whole finding. The server never consulted a list of users for either request, so the first 250 wasn't about Maria. Send QUIT and nothing has been delivered to anyone.
What comes next depends on the setup behind that host. In one version, mail for the invented address lands in a shared inbox an administrator skims once a month. Elsewhere, the server takes the message, fails to find the user, and mails a bounce notice to your envelope sender an hour later.
Why the gateway often answers for everyone
Plenty of accept-all behavior isn't a decision anyone made about recipients. Companies put a filtering gateway in front of their mail server, and unless that gateway has been given a copy of the user directory, it has no way to know who exists. It accepts everything, scans it, and hands it inward, where the real server rejects unknown users after the fact.
That matters for how you read the result. An accept-all verdict on a domain behind a gateway says nothing bad about the company or the address. It tells you the question was answered by a machine that doesn't know.
Don't confuse this with a 252 reply. A 252 is the server saying out loud that it won't verify. Accept-all is quieter: the server says a plain yes to everything, and only a control probe with an invented address reveals that the yes was automatic. The two end up in different verdicts for that reason.
Accept-all: common questions
Is accept-all the same thing as catch-all?
They describe the same situation from two angles. Accept-all is what the server does during the handshake; catch-all is how the domain is configured to route what it took.
How do you test whether a server is accept-all?
Offer it a random local part nobody could have registered. If that gets a 250, the server takes everything and your real address proved nothing.
Does accept-all mean my address is fake?
No. It means the check could not run. Plenty of accept-all domains are ordinary companies with ordinary staff mailboxes behind them.