Email Verifier
Check whether any email address is valid and deliverable before you send. emailfinder.dev connects to the recipient mail server via SMTP to confirm the mailbox exists — no test emails, no databases. Zero false positives.
How the email verifier works
Most email verifiers check a list of known-bad domains or pattern-match the address format. That catches obvious errors but misses the real problem: individual mailboxes that no longer exist even though the domain is valid.
emailfinder.dev goes further. For every verification request, it opens an SMTP connection to the recipient's mail server and sends an RCPT TO command. The mail server responds with whether the mailbox exists — without receiving an actual email. This is the same check a mail server runs when you send a real message, but run in advance.
# SMTP verification flow
→ EHLO emailfinder.dev
→ MAIL FROM: <verify@emailfinder.dev>
→ RCPT TO: <jane.doe@acme.com>
← 250 OK — Mailbox exists and is accepting messages
← 550 5.1.1 — Mailbox does not exist
Email verifier API endpoint
One GET request. Returns the verification status and reason within seconds.
Endpoint — 0 credits for invalid, 1 credit for valid
Response:
Why bounce rate matters
Every email sent to a non-existent mailbox generates a hard bounce. Email providers track your bounce rate, and if it rises above 2–3%, they start throttling your messages or routing them to spam. At 5–10%, many providers block the sending domain entirely.
Verifying your list before sending keeps bounces near zero. For sales teams, recruiters, and marketers sending high-volume campaigns, this is the difference between reaching the inbox and being blocked.
Verify emails in bulk
The email verifier API supports 1,000 requests per minute, making it suitable for verifying entire lists before a campaign launch. Run your CSV through the API, filter for status: valid, and send only to confirmed deliverable addresses.
# Verify a list of emails via the API
import requests
API_KEY = "YOUR_API_KEY"
emails = ["jane@acme.com", "john@example.com", "bad@notreal.xyz"]
for email in emails:
r = requests.get(
"https://www.emailfinder.dev/api/validate-email",
params={"email": email},
headers={"Authorization": f"Bearer {API_KEY}"}
)
result = r.json()
print(f"{email}: {result.get('status')}")Email verifier vs email finder
Email Verifier
You already have an email address and want to confirm it's deliverable before sending.
Input: an email address. Output: valid / invalid / unknown.
Email Finder
You have a name and company but no email address — you need to discover it first.
Input: name + domain. Output: verified email address.
emailfinder.dev does both. The find endpoints discover and verify in one call. The validate endpoint verifies an address you already have. See the Email Finder API →
Email verifier FAQ
How does email verification work?
emailfinder.dev connects directly to the recipient's mail server using SMTP and asks whether the mailbox exists — without actually sending a message. If the server confirms the mailbox, the email is valid. If it rejects the address, it's undeliverable. This is called SMTP verification and it's the most accurate method available.
What is the difference between email validation and email verification?
Email validation checks whether an address is syntactically correct (has an @ symbol, a valid domain, etc.). Email verification goes further: it connects to the actual mail server and confirms the specific mailbox exists. Validation can be done offline; verification requires a live network check. emailfinder.dev does both in a single call.
What does a valid vs invalid result mean?
A valid result means the mail server confirmed the mailbox exists and is accepting messages. An invalid result means the mail server rejected the address — it's undeliverable. An unknown result means the server's response was inconclusive (some servers accept all addresses without confirming them individually).
Does email verification send a test email?
No. emailfinder.dev uses an SMTP handshake (the RCPT TO command) to check the mailbox without sending any email. The mail server responds to the handshake without delivering a message, so the address owner is never notified.
How much does it cost to verify an email?
Email verification uses the validate-email endpoint at 0 credits for invalid results and 1 credit for valid results. You only pay when the verification confirms a deliverable mailbox. Credits start from €0.009 each.
Can I verify emails in bulk?
Yes. The validate-email endpoint supports 1,000 requests per minute, making it suitable for verifying large lists. Upload your CSV, loop through it via the API, and filter out invalid addresses before sending.
Why should I verify emails before sending?
Sending to invalid email addresses raises your bounce rate. A high bounce rate signals to email providers (Gmail, Microsoft, etc.) that you're sending to bad lists, which damages your sender reputation and causes your messages to land in spam — or get blocked entirely.
Related tools
- · Email Finder API — find emails by name, domain, LinkedIn, or role
- · Bulk Email Finder — enrich entire lists with verified emails
- · Domain Search — find all email addresses at a company
- · Guide: How to verify email addresses with SMTP
Start verifying emails free
Free credits included. No credit card required. 1,000 verifications per minute.