Email Verifier - Bulk SMTP & MX Validation
Under maintenancePricing
Pay per event
Email Verifier - Bulk SMTP & MX Validation
Under maintenanceVerify email addresses in bulk: syntax check, MX record lookup and optional SMTP probe. Returns validity verdict, status and sub-status, MX records, SMTP response code, disposable and catch-all detection plus timing per address. Clean lead lists, cut bounce rates and protect sender reputation.
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Pay per event
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Developer
Ryan Zinburg
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a day ago
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Email Verifier - Bulk Syntax, MX & SMTP Validation
Validate email addresses before you send to them. The actor runs three increasingly strict checks per address and reports exactly which one failed, so a bad list can be cleaned rather than discarded.
No API key, no third-party verification service.
What you get per address
| Field | Example |
|---|---|
email | info@example.com |
formatValid | syntax check result |
mxValid, mxRecords | whether the domain accepts mail, and through which servers |
smtpValid, smtpCode | SMTP probe result and the server's response code |
isCatchAll | domain accepts any address, so a positive result proves little |
isDisposable | throwaway provider such as a 10-minute mail service |
valid | the overall verdict |
status, subStatus | why that verdict, e.g. invalid mailbox, no MX, catch-all |
durationMs, verifiedAt | how long the check took and when |
Input
- emails - the addresses to check, as an array
- smtpCheck - enable the SMTP probe. Off by default, see below
- smtpTimeout - how long to wait per SMTP conversation
Example input
Use cases
- Lead list cleaning - drop invalid addresses before importing into a CRM or sending tool
- Bounce rate reduction - most hard bounces are avoidable and hard bounces are what damage sender reputation
- Signup form protection - reject disposable addresses at registration
- CRM hygiene - re-verify an ageing database, where 20 to 30 percent of addresses decay per year
- Deliverability diagnostics -
mxRecordsshows which provider a domain uses, which explains a lot about filtering behaviour - Sales operations - qualify a purchased or scraped list before paying to send to it
The three levels, and what each proves
- Format - the address is syntactically valid. Cheap, instant, catches typos.
- MX - the domain publishes mail servers, so it can receive mail at all. Catches dead and parked domains.
- SMTP - the mail server is asked whether the specific mailbox exists, without sending a message. This is the only check that says anything about the individual address.
isCatchAll is the important caveat: some domains accept every address, so an SMTP success there does not prove the mailbox exists. The actor flags that case explicitly instead of reporting a false positive.
Notes on the SMTP probe
- It is off by default on purpose. SMTP probing opens a connection to a stranger's mail server, and doing it at volume from one address can get that address rate-limited or blocklisted.
- Large providers such as Google and Microsoft deliberately answer ambiguously, so results for those domains lean on MX and catch-all detection rather than a definitive mailbox answer.
- Verify lists you have a legitimate reason to contact. In the EU, an email address belonging to a person is personal data, and cleaning a list does not by itself create a lawful basis for sending to it.
