Don't burn your domain on dead mailboxes.
SMTP mailbox probes for cold outreach and signup forms. Catch-alls stay scored, every failure gets a reason, and Unknown credits are refunded.
Bulk CSV & Excel verificationPricing from €35 for 10,000
Verify an email right now
No signup. Real SMTP probe. 3 of 3 free verifications left.
How email verification works in NexiphorVerifier
Built for sales and marketing teams who clean cold-outreach lists, CRM exports and event lists before a campaign — so dead mailboxes do not turn into bounces against your domain.
- Step 1
Add the addresses
Check one address, paste a list, or upload a CSV, TXT, Excel or PDF file. Duplicate rows are removed before checking.
- Step 2
Each address is checked
Syntax, domain and MX records, then a conversation with the receiving mail server up to the recipient step — no email is sent. A made-up address on the same domain shows whether it accepts everything (catch-all).
- Step 3
Review status and reason
Valid, Invalid, Risky or Unknown, with the reason behind it and a recommended action. Bulk jobs show live progress and a summary by outcome.
- Step 4
Export what you will send
Download everything or only the outcomes you choose, as CSV or Excel, with your original columns kept next to the result.
Trying one address first? Check an email address · Cleaning a whole file? See how bulk verification works · How SMTP verification works
What each result means — and what to do with it
Every address gets one of four statuses, a reason and a recommended action. The recommended action is the send decision, and the reason explains it: “the server said this mailbox does not exist” and “this domain accepts any address” call for different decisions.
Valid
Positive evidence for this address: either the mailbox was confirmed, or the receiving server accepted it while rejecting a made-up address on the same domain.
What to do: Safe to send when the mailbox was confirmed. Send with caution when the server accepted the address without confirming the mailbox.
Risky
There is a reason for caution. For example, a catch-all domain accepts any address, so acceptance alone does not confirm this mailbox. Providers that accept without confirming, mailboxes that are full right now, and policy signals such as toxic domains or possible spam traps also land here.
What to do: Send with caution, Review before sending or Try again — each row states which, and why. A catch-all domain's acceptance on its own is never treated as mailbox confirmation.
Invalid
A reason not to send — for example the server said the mailbox does not exist, the domain has no working mail route, or the domain is disposable. A disposable domain is a policy classification, not proof that the address cannot receive mail.
What to do: Do not send. Remove the address, or fix it when a likely typo correction is suggested.
Unknownshown as “No reliable result” in the dashboard
No reliable answer: the server timed out, deferred or blocked the check. It says nothing about whether the address is good or bad.
What to do: Follow the row's action: try again later, or review it before sending when the server blocked the check. If a charged check finishes as Unknown, that credit is refunded automatically.
A check talks to the receiving mail server without sending a message. Acceptance at that stage does not guarantee inbox placement — spam filtering happens later, when you actually send. Scores rank results; they are not delivery probabilities. Results also age, so re-check a list that has been sitting for months.
More detail: Valid vs Invalid vs Risky vs Unknown · What is a catch-all domain? · Try the email checker
The 
Advantage
The differences you will notice in the results, the export and the bill.
We Don't Guess Valid
Unknown means the provider withheld a definitive answer — not that the address is bad. We refuse to guess (protecting your reputation) and refund those credits automatically.
Clear Failure Explanations
Reason codes per email: syntax, blocked, greylisted, temp fail—no guessing.
Real-time Bulk Progress
Watch each job fill in live, and download finished rows before the whole file is done.
Honest Catch-all Scoring
Catch-alls stay Risky with provider-graded confidence — we won't mark them Valid to inflate your list.
Scheduled List Verification
Connect Instantly, Smartlead, or Lemlist — auto sync, verify, and push on a schedule. HubSpot and other CRMs available in Beta.
Built for Large CSVs
Stable uploads + resilient processing for big lists, with exports grouped by the same outcomes you see on the job page.
Opt-in Auto-Delete
Results stay in your workspace unless you opt in. When enabled, results and uploaded addresses are deleted automatically after the window you set (1 hour to 90 days; 24 hours if you don't change it).
Opt-in Sync Verify API
Need the result in one HTTP call? Pass wait=true (or X-Nexiphor-Wait) on single verify — built for Zapier and scripts.
Ready to experience the difference? See it in action
Built for operators who need to know why
MillionVerifier competes on bulk price; ZeroBounce sells a wider deliverability suite. We focus on the verification itself: a reason on every result, catch-alls kept out of Valid, and Unknown credits returned.
Unknown results
- NexiphorVerifier
- Credit returned automatically
- MillionVerifier
- Marketed as a refund for risky emails; terms describe discretionary goodwill credits
- ZeroBounce
- Not charged
Published pay-as-you-go price
- NexiphorVerifier
- €35 for 10,000 (EUR)
- MillionVerifier
- $89 for 50,000 (USD)
- ZeroBounce
- $39 for 2,000 (USD)
| What you pay for | NexiphorVerifier | MillionVerifier | ZeroBounce |
|---|---|---|---|
| Unknown results | Credit returned automatically | Marketed as a refund for risky emails; terms describe discretionary goodwill credits | Not charged |
| Published pay-as-you-go price | €35 for 10,000 (EUR) | $89 for 50,000 (USD) | $39 for 2,000 (USD) |
Checked on 16 October 2026 against ZeroBounce's pricing page and MillionVerifier's homepage, help centre and terms. Prices: our smallest pack, ZeroBounce's stated minimum purchase, and the 50,000 example on MillionVerifier's homepage — each in its own currency. Vendor terms change — check them before you decide.
Full comparisons: NexiphorVerifier vs ZeroBounce · NexiphorVerifier vs MillionVerifier
Pay for the addresses you actually check
One credit per address. Buy a pack when you need one — there is no subscription, and unused credits stay on your balance.
Credit packs
One credit, one address checked
Packs are one-off purchases in EUR. If a check ends Unknown, the credit goes back to your balance.
- Single address checks
- CSV, Excel or pasted lists
- A reason on every result
- Unknown results refunded
- Credits don't expire
- Catch-alls stay Risky
Choose a pack size
10,000 credits
See every pack and what uses a credit€0.0035 per address
Buy credits100 free credits on signup. Unknown results return to your balance automatically.
Privacy You Can Trust
Your data security is our top priority. We've built NexiphorVerifier with privacy at its core.
Zero-Storage Mode
Off unless you turn it on; until then, results stay in your workspace. When enabled, results and uploaded addresses are deleted automatically after the retention window you set (1 hour to 90 days; 24 hours if you don't change it). Billing records and job totals are kept.
GDPR-Ready Practices
Built with GDPR principles: data minimisation and deletion controls, with a published data processing agreement.
TLS Encryption
All data encrypted with TLS during transmission.
No Data Reselling
We never sell, share, or train models on your data.
Start with 100 free credits No card required
Check addresses in the browser now, upload a list when you are ready, and buy credits only when you need more.