How to verify an email address without sending an email
Check whether an email address is safe to send to before you send anything. What deliverable, risky and undeliverable mean, why catch-all domains are tricky, and how to check a list.
Every email that bounces costs you more than one lost message. Mailbox providers watch how often your mail bounces, and a sender with a high bounce rate starts landing in spam, even for the people whose addresses were fine. So the best time to find a bad address is before you send to it.
The obvious test, sending a "test" email and waiting to see what happens, is exactly what you want to avoid. This guide explains how to check an address without sending anything, what the answers mean, and what to do with each one.
Why checking first matters
- Bounces hurt your sender reputation. Keep hard bounces well under 2% of what you send. A list with 10% bad addresses can undo months of careful sending.
- The people you check should not hear from you yet. A good check never emails the address it is checking, so nobody gets a strange message, and nobody marks you as spam before you have said anything.
- Bad addresses cost money. Every email sent to a dead address is a credit, a sending slot and a bit of reputation spent for nothing.
What a good check tells you
Barometer answers with one of four verdicts, a confidence score from 0 to 100, and the reasons in plain language.
| Verdict | What it means | What to do |
|---|---|---|
| Deliverable | The mailbox exists and the address fits the person. | Send. |
| Risky | It may work, but something is uncertain. | Add context and check deeper, or decide by hand. |
| Undeliverable | Mail to this address will not arrive. | Do not send. |
| Unknown | No confident answer right now. | Try again later. Unknown checks are free. |
The reasons matter as much as the verdict. "The domain no longer receives mail" and "this is a shared team inbox" are both reasons not to send, but they call for different next steps.
The hard cases
Most addresses are easy to judge. These are the ones that are not.
Catch-all domains
Some companies accept mail for any address at their domain, real or not. You cannot tell from the outside whether jane@company.com is a real person or will be quietly dropped. A good check does not stop at "the domain accepts it". It looks for evidence that the address belongs to the person you think it does: their name, their company, and where you found the address.
That is why context helps. Pass the person's name, company and the page where you found them, and Barometer can judge a catch-all address instead of just calling it risky.
Shared inboxes
Addresses like info@, hello@ and sales@ usually work, but they reach whoever reads the shared inbox, not the person who decides. They are fine for a small business where the owner reads everything, and a poor bet at a large company. Barometer flags them so you can choose.
Full mailboxes
A mailbox that is full rejects new mail, and a full mailbox usually means nobody is reading it. Barometer treats it as undeliverable.
Free and throwaway addresses
Personal webmail addresses can be real buyers, especially at small companies. Throwaway addresses, made to get past a sign-up form, almost never are. Your own policy decides which of these you allow.
Set your own rules
On top of the verdict, you can set a policy: block shared inboxes, skip certain domains or top-level domains, or allow free webmail. The answer tells you whether the address passes your rules, so you do not have to filter by hand afterwards. The docs list every option.
Check one address or a whole list
- In the browser: sign in, add the people you want to check to your list (paste them one per line), and check them in one go. Each person shows their verdict and the reasons.
- From a terminal:
npm install -g stormgtm, thenstormgtm check jane.doe@acme.io --name "Jane Doe" --company Acme. Add--deepfor a closer look at hard cases. - From your code or agent: one API call per address, or a batch of thousands with a webhook when it is done. See the quickstart.
Tell it what happened
After you send, report what happened: delivered, bounced or replied. Reporting is free. Real outcomes are the best evidence there is, and they make every later check on your account sharper.
What it costs
A fast check costs 1 credit, and a deep check, which looks harder at the person behind the address, costs 5. Unknown results are free, so you only pay for an answer. New accounts start with up to 100 free credits, and packs never expire. See pricing.
The short version
Check before you send, never by sending. Send to deliverable, think twice about risky, drop undeliverable, and retry unknown for free. If you need the leads too, Radar can find them from your website and pass them straight to Barometer.