Privacy-focused
email bounce checker

BlockSurvey's free email bounce checker is a privacy focused tool. It helps you to find if an email is valid or not! Simply enter email addresses and click the "Verify" button and Email Bounce Checker will check the email for each address.

Enter an email address(s)

Need to check more than 10 emails? Contact us at [email protected].

SMTP

Know how the privacy-focused
email bounce checker works

We don't like email bounces. You don't like email bounces. So we've built the best privacy-focused bounce checker out there, so we can keep our open rates high and your response rate even higher. Our privacy-friendly email checker uses open source libraries to determine if an email bounced. Emails are not logged, not tracked. If you need to store or compare an address later without keeping it in the clear, turn it into a one-way hash and keep only the digest. It's open source and you can host it as well

Step 1 : Regex and Typos

Blitzkrieg, thats the pace of the world around us, a few pattern and typo errors may occur, so we begin our checks here.

Step 2 : Disposable

Our second check is for those using burner emails, disposable emails, etc.

Step 3 : MX and SMTP

Finally, we get a tad more technical and perform the traditional Server checks.

What we do — and don't — with what you submit

A real inbox check needs a real connection to the destination mail server, so we're upfront about where that step runs and what happens to your list afterwards.

Fast checks run first

Regex syntax, common typos, and disposable-domain matching happen before anything else, so addresses with an obvious pattern error or a burner domain are flagged without needing the slower MX/SMTP step at all.

MX and SMTP checks run on our server, by necessity

A browser tab cannot open a raw SMTP socket to a mail server, that's a restriction of the browser itself, not a design choice. So when regex and typo checks pass, the addresses are sent to a BlockSurvey server to look up MX records and, if the SMTP checkbox is on, simulate sending a mail. That's the only way to find out if a mailbox is actually reachable.

Nothing logged, nothing stored

The addresses you enter are used only to run that one verification request. They are not logged, not stored, and not tied to an account, there isn't one. Close or refresh the tab and the results are gone; nothing sits in a database afterwards.

The tool itself is also open source on GitLab, so you don't have to take our word for how the checks run.

Built for anyone cleaning up a list

Checking a handful of addresses before they go anywhere shouldn't require an account or a credit card.

Marketers & growth teams

Catch typos and dead addresses in a segment before a campaign goes out, so a send doesn't take a hit to open rates or sender reputation over a handful of bad rows.

Developers

Spot-check a signup or checkout flow for disposable domains and malformed addresses while you're still building the form, instead of finding out from a bounce report later.

Anyone who doesn't want to upload a list to a marketing SaaS

A free, no-account check for a short list, without handing it to a platform that keeps it. If the list itself needs to travel further, encrypt it in your browser before you send it to anyone.

Want to create secure online forms and surveys?

BlockSurvey runs on zero-knowledge surveys, so responses are encrypted on the respondent's device and the server stores nothing readable.

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These tools run in your browser because that is how we build everything. The same idea, applied to research: privacy-first surveys with end-to-end encryption.

GitLab

Frequently asked questions

What is an email bounce?

An email bounce is an automated message from an mail server that informs the sender that their email has not been delivered to its intended destination. This will indicate that something has gone wrong either on the sender side or the recipients’ side.

Is it safe to use a free email bounce checker?

The tool offers 100% privacy as at no point the entered data is logged or stored to our servers. The bigger risk is what happens to the list afterwards, so encrypt the contact list in your browser before you send it to anyone.

How many emails can I verify at a time?

As of now the tool sets a limit of 10 emails for a single go.

What are the types of email bounce status returned?

The tool returns three type of statuses :

No bounce : Means that the email addresses are valid.
Soft bounce : Means that the email addresses are temporarily unavailable. The tool returns this error for all kinds of errors from typos, patterns, SMTP validation failing due to unknown causes or mail server unavailability, etc.
Hard bounce : Means that the email addresses are permanently unavailable. The tool throws this error when no MX records of the given addresses are found.

What is SMTP validation and what are the email providers supported?

The tool performs SMTP validation when the SMTP checkbox is checked and vice versa. The SMTP validation involves establishing a socket connection with the mail server and simulating the sending of an email. This being the most trickiest part of the entire validation process can return false negatives cause of certain settings at the mail server end(Most mail servers have some sort of checks to block spam). The tool has returned successful SMTP validation checks for the following domain names :
google.com, yandex.com, yahoo.com.
If your list to be checked includes other domain names there is a high chance of getting false negative results (Soft bounce warning mostly) for even valid email addresses if the SMTP flag is set.

Is BlockSurvey email bounce checker open source?

Yes, the tool is open source and the links to the source code can be found in the app page.

Is this email bounce checker a honey pot?

Here at BlockSurvey, we give at most importance to privacy which is consistent with our vision of a world having a decentralized internet space. As already mentioned above, the tool does not collect and store any form of data given to it. It simply acts as a platform for people to enter their emails and get them validated.

Why is it free?

The product is built from already existing open source code with slight tweaks by us. It was primarily built for weeding out burner and disposal emails from our own product i.e. BlockSurvey and at a certain point we had this idea of sharing the benefits accruing from this project with the rest of the world.

What are the modules used to build this?

The tool uses a npm module called "deep-email-validator".
link : https://www.npmjs.com/package/deep-email-validator.

How does email bounce checker work?

The tool checks for Regex, Typos error as a first step and then goes to check if the email address is present within the list of disposable email domains, then comes the check for the MX record followed by the SMTP check(if the flag is set). The tool returns a status of 'No bounce' if all the checks return true and in case of error based on the error type we return the status of either 'Soft bounce' or 'Hard bounce'.

How is this different from a paid email verification service?

Paid bulk-verification services like ZeroBounce or NeverBounce run the same style of check under the hood, MX lookups and SMTP handshakes, but they ask you to create an account, charge per credit, and often keep a copy of the list you upload. This tool runs the same regex, typo, disposable-domain, MX, and optional SMTP checks for free, with a 10-email-per-batch cap, no sign-up, and nothing logged or stored on our end. If you need to verify thousands of emails in one go, a paid service with a larger batch size will still be the faster option.

What happens if the SMTP check times out or can't get a clear answer?

Mail servers rate-limit, greylist, or silently drop verification probes to fight spam, so the socket connection does not always get a clean yes or no back. When the SMTP step can't reach a definitive answer, the tool does not guess: it returns 'Soft bounce' so you know the result is unconfirmed rather than treating the address as invalid. If you keep seeing soft bounces for addresses you know are real, try again later or re-run the check with the SMTP checkbox off to get a pattern and MX-only read.

Know how the privacy-focused email bounce checker works