1. Why a new temp-mail address looks legitimate
The domain changes. The inbox gateway does not.
Services such as temp-mail.org do not reuse a single public burner name. Each inbox is issued on a fresh domain. That name has never appeared on a public disposable list, so a lookup that only compares the domain string returns clean.
Opening the domain in a browser often fails because it publishes no website address. It does publish mail, and the mail host answers on a stable gateway. Treating “no website” as disposable would also flag parked brands, internal mail domains, and new companies that have not launched a site yet.
A match is one confirmed mail gateway, not the address next to it and not the cloud range it sits in. Those ranges are shared with legitimate mail.
2. The check that actually holds
Resolve the MX host, then match an exact IP
After syntax and MX lookup, BounceLayer resolves the A records of the mail hosts. If one of those addresses is a confirmed temp-mail gateway, the result is disposable: status do_not_mail, reason disposable, confidence 95. SMTP is not opened, so the verifier does not talk to the burner server.
Hosts that belong to major mailbox providers are skipped before any IP test. A Google or Microsoft MX is never marked disposable because it shares a data-center neighborhood with something else.
- Single verify and the homepage demo run the check on a live verification.
- Bulk upload runs it for every row, including a Redis hit that was stored before the rule existed.
- Risk Intelligence scores the same hit as disposable and risky, without an SMTP probe.
- The public email checker applies it after the MX lookup.
| Signal | Rotating inbox | Used as a verdict? |
|---|---|---|
| Domain on a disposable list | No | Misses rotating names |
| Website address | None | Clue only |
| MX hostname | A fresh mail host | Not enough on its own |
| Mail-server address | Confirmed gateway | Yes, exact match |
| Neighboring address | Different host | No |
| Major provider MX | Google or Microsoft | No |
3. What this does not claim
High precision on a confirmed gateway, not every burner on the internet
Accuracy here means few false positives. An address is flagged only when its mail server is a gateway we have confirmed as temp-mail. A new provider on a different server is a miss until that gateway is confirmed. A domain that later moves off the gateway stops matching, which is the correct outcome.
Name lists still catch the well-known burners (mailinator, yopmail, guerrillamail, and the rest of the bundled set). The IP check is the extra layer for domains those lists have never seen.
A disposable verdict means do not mail it and do not treat the signup as a real customer. It does not mean the mailbox failed an SMTP rejection. The probe was skipped on purpose.
4. Where to run it
Same rule on every verification surface
Paste a single address on the verifier, drop a CSV in bulk upload, or open Risk Intelligence. A rotating temp-mail inbox on this gateway comes back disposable in each of those places, including when an older cached result is read back.
If you only need a fast syntax and MX look, the public email checker reports the same disposable flag without a mailbox probe.
{
"email": "inbox@rotating-domain.example",
"status": "do_not_mail",
"is_disposable": true,
"is_valid": false,
"confidence_score": 95,
"status_reason": "disposable",
"smtp_checked": false
}