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

{
  "emails": ["info@github.com", "support@stripe.com", "nobody@example.invalid"],
  "smtpCheck": true,
  "smtpTimeout": 8000
}

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 - mxRecords shows 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

1. Format - the address is syntactically valid. Cheap, instant, catches typos.
2. MX - the domain publishes mail servers, so it can receive mail at all. Catches dead and parked domains.
3. 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.