Does this domain accept every address?
Catch-all servers accept mail for any mailbox, valid or not. We test each domain with a random address that cannot exist.
How to test if a domain is catch-all: connect to its mail server over SMTP and
issue RCPT TO for an address that cannot exist. If the server accepts it, the domain
is catch-all (accept-all), which is exactly what this tester does.
What a catch-all probe looks like on the wire
An example SMTP session against an accept-all server. The tell is in the
RCPT TO response: a normal server rejects an address that cannot exist, a
catch-all server takes it.
$ telnet mail.example-corp.com 25
220 mail.example-corp.com ESMTP ready
>> HELO tester.example
250 mail.example-corp.com
>> MAIL FROM:<[email protected]>
250 2.1.0 OK
>> RCPT TO:<[email protected]>
250 2.1.5 OK ← accepted: this domain is catch-all
>> QUIT
221 2.0.0 ByeNo message body is ever sent. The probe stops at the
RCPT TO handshake, so nothing lands in any inbox.
How the Catch-All Test Works
Six steps separate a bare domain name from a classification you can act on. Nothing is delivered along the way, and the whole sequence finishes in seconds.
MX Resolution
We resolve the domain's MX records. No records means there is no mail service at all.
SMTP Connection
We connect to the mail server exactly like a sending program would.
Impossible Mailbox Probe
We ask about a random address nobody could ever have registered.
RCPT TO Verdict
The server's acceptance of obvious nonsense reveals its receiving policy.
Classification
The domain is filed as normal, accept-all, no-MX or disposable.
Handling Guidance
You learn what the outcome means for the addresses on your list.
What One Probe Tells You
A single check against an impossible mailbox returns several findings at once: the domain's receiving policy, its mail setup and what both mean for the people listed behind it.
Accept-All Detection
Spots servers configured to take every address, so an accepted probe never gets mistaken for proof that a specific mailbox exists.
Normal-Server Confirmation
A server that rejects behaviour means mailbox-level verification is reliable, and your regular per-address results can be trusted.
Missing MX Records
Domains without mail servers cannot receive mail at all. The probe catches them before a single send is wasted.
Disposable Domains Flagged
Temporary email providers trip the same test, so throwaway domains never slip onto your list unnoticed.
Zero Inbox Impact
The handshake stops early and nothing is delivered. No test message arrives, bounces or bothers anyone at the other end.
Risk Framing
Each outcome comes with plain guidance on how to treat the addresses behind an accept-all server, from trusted to segment-and-watch.
Two Servers, Two Very Different Answers
The same random probe produces opposite verdicts depending on how a domain is configured. These examples are illustrative; run the checker above for live results.
sales@northwind-traders.example
- Random probeAccepted
- ClassificationAccept-all
- Mailbox proofImpossible via SMTP
jane@brightline-studio.example
- Random probeRejected
- ClassificationNormal
- Mailbox proofPossible
Why Accept-All Domains Deserve Their Own Test
An address behind an accept-all server looks perfectly healthy right up until your first campaign, when bounces surface silently and personalisation written for that contact is wasted. Some recycled catch-all domains double as spam traps, so mailing them puts your sender reputation on the line. A dedicated probe turns that unknown into a segment you control before anything is sent.
Segment Instead of Deleting
Addresses behind these servers often belong to real people. Flag the domain and give the group its own segment rather than cutting genuine contacts.
Avoid Invisible Bounces
Bounces on these domains only show up after sending. Knowing the policy upfront keeps nasty surprises out of your post-campaign report.
Smarter Outreach Calls
Skip accept-all accounts entirely or send a re-permission message first, instead of burning attempts on addresses nobody can confirm.
Honest Verification Coverage
Understand precisely what verification can prove and where it stops, so your data quality claims survive scrutiny.
Where Teams Put the Catch-All Test to Work
Select a team to see how one domain-level probe changes the working process.
Campaign prep workflow
- Subscriber export arrives from your ESP
- Addresses grouped by sending domain
- Each domain probed with a random mailbox
- Accept-all domains split into their own segment
Prospecting workflow
- Likely patterns generated for the prospect's name
- Company domain tested with the random probe
- Accept-all servers skipped, since guesses cannot be confirmed there
- Surviving candidates validated mailbox by mailbox
Source grading workflow
- Imported contact source staged for review
- Sample of domains run through the probe
- Source scored by its share of accept-all results
- Only graded sources feed downstream tables
Migration audit workflow
- Hard-bounce domains pulled from the spike window
- Each domain re-tested after the migration
- Policy changes separated from genuinely dead domains
- Client advised to segment before the next send
Gate Signups on the Catch-All Flag
One GET request returns the full signal set for an address, catch_all included. Where the response reports catch_all true, reject the registration outright or route it into a manual review queue, before the account ever reaches your product.
Response fields
curl -G "https://api.emails-checker.net/check" \ -d "access_key=YOUR_ACCESS_KEY" \ -d "[email protected]"
$response = Illuminate\Support\Facades\Http::get(
'https://api.emails-checker.net/check',
[
'access_key' => 'YOUR_ACCESS_KEY',
'email' => '[email protected]',
],
);
$result = $response->json();
const params = new URLSearchParams({
access_key: "YOUR_ACCESS_KEY",
email: "[email protected]",
});
const response = await fetch(`https://api.emails-checker.net/check?${params}`);
const result = await response.json();
import requests
response = requests.get(
"https://api.emails-checker.net/check",
params={
"access_key": "YOUR_ACCESS_KEY",
"email": "[email protected]",
},
)
result = response.json()
Example response shape:
{
"success": true,
"response": {
"email": "[email protected]",
"result": "deliverable",
"syntax": true,
"mx_records": true,
"catch_all": false,
"disposable": false,
"role": false,
"free_email": false,
"domain": "company.com"
}
}
Mailbox-level probes on accept-all domains come back unknown or risky in the platform.
One Probe or Every Address You Own?
The tester above checks a single domain per lookup. Emails Checker runs the same classification over entire lists and automated jobs, alongside full SMTP mailbox verification.
| Capability | Free CheckerThis page | Emails CheckerFull platform |
|---|---|---|
| Domain status check | Yes | Included on every address |
| Catch-all classification | Yes | Yes |
| Full SMTP mailbox checks | Not on this tool | Yes |
| Disposable detection | Included | Included |
| Scope | One domain at a time | Whole lists and automated jobs |
| Account required | No | 100 free credits on signup |