Free tool
Email existence checker. Find out if a mailbox exists.
Need to check existence on every signup or clean a list? Use the API
Trueguard Basic is free
Run the same check at scale.
Use it through the API to check signups, lead forms and email lists.
Create a free accountNo credit card required.
Check whether a mailbox exists.
10 free checks a day, no signup and no card. Nothing is sent to the address you check.
Or try
Hard bounces
Mail to a mailbox that does not exist fails for good. Send enough of it and providers throttle your domain.
Invented addresses
People type made-up addresses to get past a form. The format passes, but no mailbox sits behind it.
Stale contacts
Mailboxes get deleted when people change jobs. An address that worked last year can bounce today.
How do I check if an email address exists?
The mailbox answers for itself. We just ask, and stop before sending.
Resolve the MX records
Open an SMTP handshake
Read the server's answer
What each result means.
Every answer, in plain English.
The mailbox exists. The mail server confirmed this exact address, or a second check did when SMTP could not.
The server accepted the address, with a caveat: the domain accepts every address, the inbox is full, or the address is throwaway or shared.
The mailbox does not exist, the domain has no mail servers, or the address is not written correctly. Mail to it will bounce.
The server would not say if the mailbox exists. Some providers block these checks, so confirm the address with an activation email.
Three quick definitions.
What does it mean for an address to exist?
That the destination mail server accepts mail for that exact mailbox. The address can be perfectly formatted at a domain with working mail servers and still not exist, because the mailbox was never created or has since been deleted.
What is a hard bounce?
A permanent delivery failure: the server says the mailbox does not exist and will never accept mail for it. Hard bounces are what an existence check is for. Soft bounces are temporary conditions like a full mailbox or a server that is briefly unavailable.
Why can existence not always be proven?
Catch-all domains accept every address, so the server's answer says nothing about one mailbox, and the address is risky unless a second check resolves it. Some providers also block verification checks, and then we return unknown rather than guess.
When should you use the API instead of this page?
The API returns the same signals plus structured fields and 50,000 monthly validations on the paid plan. The free tier is 100 a month, no card.
One address, by hand
This page
A handful of leads from a CSV
This page, or the API with a 10-line scriptEvery signup, every form submit
Email validation API. Call it from your backend.Hundreds of thousands a month
Email validation API, Standard plancurl -X POST https://api.trueguard.io/v2/email/validation \
-H "X-API-KEY: $YOUR_KEY" \
-H "Content-Type: application/json" \
-d '{"email":"name@example.com"}'Questions about mailbox existence.
Still stuck? Contact support or read the documentation.
Can you tell if an email exists without sending anything?
Usually, yes. The SMTP handshake asks the destination server whether it would accept mail for the address, then stops. The server's answer is the evidence. No message is queued or delivered.
What happens with a catch-all domain?
A catch-all accepts mail for every address at the domain, so SMTP gives the same answer for a real mailbox and a random string. We return risky, unless a second check that does not use SMTP confirms or rules out the mailbox. Then you get safe or invalid.
Does a valid result guarantee delivery?
It means the mailbox accepted the check at that moment. Mailboxes fill up, get suspended and get deleted, so an address confirmed today can bounce next month. Check close to the moment you send.
Can the mailbox owner see the check?
No. Nothing is delivered. Some mail servers record probe attempts in their own logs, but no end user is notified.
Is there an API for this?
Yes. The same check runs through the email validation endpoint, 100 validations a month free, no card. One request returns existence along with the disposable, catch-all, role and free-provider flags.
Further reading
Check existence on every signup.
The same check runs through our validation endpoint. 100 free a month, no card. Same accuracy, same response shape, ready to drop into your backend.
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