Is this email domain disposable? Check one that is not on any list
You see a signup from nmailbox.cc or nullsto.edu.pl. No list you own mentions it. Is it a throwaway inbox service or a small company? A static list can never answer that for new domains, because temp-mail services register fresh domains constantly. This page gives you a quick manual check: paste one or more domains and it looks up their mail servers (MX records) live, then shows which domains share the same mail host. It also lists the other signals worth checking and says plainly what none of them prove.
Signals worth checking, and how far to trust them
| Signal | What it suggests | Why it is not proof |
|---|---|---|
| Several unfamiliar domains point to the same MX host | One operator runs many domains. Temp-mail services do this to rotate domains when the old ones get blocked. | Hosting providers and Google Workspace or Microsoft 365 are shared by millions of legitimate domains. Only an unusual, small shared host is a signal. |
| The MX host is a subdomain of the domain itself | The domain runs its own mail server. Common for inbox-on-a-website services. | Plenty of small companies and individuals self-host mail. |
| The domain has a public website offering free inboxes | Strongest signal: open the domain in a browser and read the home page. | Requires a human look. Do not visit domains you do not trust from a work machine without care. |
| Registered very recently | Throwaway services churn domains. Look the domain up with a WHOIS or RDAP tool. | New businesses are new too. |
| Name looks like a tempmail brand (temp, trash, 10min) | Often right. | Names are cheap to fake in either direction. |
What to do with a domain you cannot classify
Do not block on suspicion alone. A reasonable pattern: accept the signup, mark it unverified, and require email confirmation before any value is delivered. If the address never confirms, nothing is lost. If you do confirm a domain is a throwaway service, add it to your block list, and keep that list as data you can update without a deploy. Our disposable domain list shows a starting point of 284 domains, and it does not contain every domain you will meet. It does not currently list the two examples above, and we have not verified what either one is.
Automating the first pass
The MailGate API does the same MX lookup plus syntax, role-account, typo and disposable-list checks in one call, so you can run it at signup time:
curl "https://pw-d20261007a2.plainwork-apps.workers.dev/[email protected]"
# {"disposable":false,"mx":"ok","mx_hosts":["mail.nmailbox.cc"],"score":100,"verdict":"deliverable", ...}That response is the honest picture: this domain has working mail servers and is not on our list. It cannot tell you whether it is a throwaway service. Free tier: 20 checks a day, no signup, on the live tester. Unlimited and bulk checks are on the $5/month plan. Related: blocking disposable signups, regex vs MX check.