Syntax and format
Validates every address against RFC 5321 and 5322, catching typos, stray spaces, and broken formatting before anything else runs.
Email Verification Service
Email Verification That Stops Bounces Before You Hit Send
Verify email addresses one at a time or 10,000 a minute. Verifox runs 9 checks on every address, including the catch-all resolution most email verification tools skip, and returns valid, invalid, or risky with a confidence score in about 380ms.
4 of 4 free verifications remaining today
4 free checks a day · No signup · Processed in memory, never stored
Trusted by 500,000+ GTM teams
2.1B+
Emails verified
99.99%
Benchmark accuracy
~380ms
Median single check
10,000/min
Bulk throughput
The basics
What is email verification and how does it work?
Email verification is the process of confirming that an address can actually receive mail before you send anything to it. A real verifier starts with format: does the string obey RFC 5321 and 5322. Then it checks the domain: does it exist, and does it publish MX records pointing at a live mail server. The decisive step is the SMTP handshake, where the verifier opens a conversation with that server and asks whether the specific mailbox exists, all without sending a message. Around that core, Verifox layers risk signals: disposable-domain matching, role addresses like info@, domain age, and whether the domain publishes SPF, DKIM, and DMARC authentication records.
The hard case is the catch-all domain, a server configured to accept mail for any address whether the mailbox exists or not. Ask it “does jane@ exist?” and the answer is always yes, which is why cheap tools mark whole companies “unknown” and move on. Between 20 and 40% of a typical B2B list sits on catch-all domains, so an email verification service that punts on them is verifying the easy two-thirds of your list. Verifox scores catch-all addresses individually with AI-confidence analysis; you can watch it work on the catch-all email checker.
When should you verify email addresses? Three moments: before any campaign that touches your sender reputation, at the point of signup through the API so bad data never enters your database, and on a monthly schedule for lists you mail regularly. For a quick spot check of a single address, the free email checker runs the full engine 4 times a day without an account.
The Verifox engine
The 9 checks behind every verified email address
Format checkers stop at the @ sign. Verifox runs all nine of these on every address, every time, and the verdict carries a confidence score you can act on.
Domain and MX records
Confirms the domain actually exists and publishes MX records pointing at a live mail server.
SMTP handshake
Opens a conversation with the mail server and pings the specific mailbox, without ever sending a message.
Disposable-domain match
Flags throwaway addresses from known temporary email providers before they pollute your list.
Role-address detection
Identifies generic inboxes like info@ and support@ that are rarely read by one person and rarely convert.
Catch-all detection
Detects servers configured to accept mail for any address, the trap where format checkers stop working.
AI-confidence scoring on catch-allsDIFFERENTIATOR
Scores each catch-all address individually using delivery and behavioral signals, instead of marking the whole domain unknown.
Domain age
Weighs how long the domain has existed. Week-old domains correlate strongly with spam operations and fake signups.
Email authentication
Checks for published SPF, DKIM, and DMARC records, a fast proxy for whether the domain is run seriously.
How it works
How to verify an email list in three steps
01
Upload or connect
Drop a CSV, Excel, or TXT file, paste addresses directly, or wire the REST API into your signup flow. Lists of 100 or 10 million both work.
02
Nine checks per address
Syntax, domain and MX, SMTP handshake, disposable match, role detection, catch-all detection, AI-confidence scoring, domain age, and authentication records run in parallel at roughly 10,000 emails per minute.
03
Act on tagged results
Every address comes back valid, invalid, or risky with a confidence score. Download the clean CSV, drop invalids, and decide on riskies with the score in front of you.
The check most tools skip
Catch-all resolution is where 20 to 40% of B2B lists fail
A catch-all server accepts every address you throw at it. Send to john@example.com? Accepted. Send to asdfghjkl@example.com? Also accepted. The standard SMTP question stops working, so most verification tools mark the entire domain “accept-all” and walk away.
Those unresolved addresses stay on your list looking verified while a chunk of them are dead. That is the gap where 20 to 40% of B2B email lists fail, and it lands hardest on sales teams, because corporate domains are exactly where catch-all configuration is common.
Verifox built an AI-confidence engine for this case. Instead of asking the server a question it answers dishonestly, the engine weighs delivery history, domain reputation, and mailbox activity signals, then scores each address individually. You get a per-address verdict on catch-all domains instead of a shrug.
Other tools
Verifox
john@example.comUnknown
john@example.comValid (94%)
jane@example.comUnknown
jane@example.comValid (87%)
asdf@example.comUnknown
asdf@example.comInvalid (12%)
test@example.comUnknown
test@example.comInvalid (8%)
mike@example.comUnknown
mike@example.comRisky (51%)
Do the math
How many of your sends never reach a mailbox?
Plug in your list size and current bounce rate. The calculator shows the sends going nowhere today, the deliverability lift a clean produces, and the exact number of credits a full clean costs. Region-specific credit prices live on the pricing page.
Your numbers
The model assumes a residual 1% bounce rate after cleaning, because lists keep decaying between the day you verify and the day you send. We never promise zero.
Before verification
Bounced emails per send2,100
Dead sends per year100,800
After verification (modeled)
Bounce rate~1%
Deliverability lift+3.2 pts
Wasted sends recovered per year76,800
Credits to clean this list once50,000
Built for senders
Who relies on an email verification service
Anyone whose revenue touches an inbox. The workflows differ; the failure mode, a burned sending domain, is identical.
Email marketing teams
Mailbox providers throttle domains that bounce. Verifying before each campaign keeps hard bounces near zero so opens reflect your content, not your list hygiene. Most teams start by running their worst segment through the free email checker.
Sales and outreach teams
Cold outreach dies fastest at catch-all corporate domains. Verify prospect lists before they hit your sequencer, and fill gaps with the email finder instead of guessing patterns.
Agencies managing client lists
Every client list you mail is a reputation you are renting. Batch verify each one through the multiple email checker or the bulk uploader before a single send goes out under your infrastructure.
Developers and product teams
Verify at signup with one call to the REST API, about 380ms median, and keep fake accounts out of your activation metrics. Building agents? The MCP server exposes the same engine as native tools.
List hygiene
Six habits that keep your email list clean
Verification works best as a routine, not a rescue. These are the habits we see in teams whose bounce rates stay under 1% year-round.
01
Verify before every campaign
A list verified last quarter is not a verified list. People change jobs, mailboxes fill, domains lapse. Re-run the list before any send that matters to your sender score.
02
Verify at the point of capture
Real-time checks on signup forms stop typos and disposables from ever entering your database. The verification API answers in about 380ms, and FoxGuard does it without writing code.
03
Prune role addresses
info@, admin@, and billing@ inboxes are shared, filtered, and almost never owned by your actual buyer. Keep them out of nurture sequences even when they verify as deliverable.
04
Never ship addresses marked unknown
If a tool labels part of your list “accept-all” or “unknown,” those addresses were not verified. Resolve them with the catch-all email checker before they resolve themselves as bounces.
05
Watch your domain, not just your list
Clean lists cannot save a blacklisted domain. Run a periodic email blacklist check on your sending domain so reputation problems surface before open rates crater.
06
Track bounces after every send
Verification is maintenance, not a one-time fix. Review every campaign with the email bounce checker and schedule a re-verification whenever the rate passes 1%.
Pricing
Pay per verification. No subscriptions. No surprises.
Credits are pay-as-you-go and they never expire, so a list clean in January and a campaign in June draw from the same balance. Every account starts with 1,000 free credits, or 2,500 when you sign up with a work address, and no card is required to claim either.
Volume discounts deepen as usage grows, and exact credit prices are localized to your region, which is why we publish them in one place instead of hard-coding numbers here. Every tier includes the full 9-check engine, catch-all resolution, bulk CSV upload, and API access.
Trust & compliance
Enterprise-grade security and scale
Every layer of the stack carries a third-party attestation, so you can ship into regulated industries without rebuilding your compliance posture.
SOC 2 Type II
Independently audited to the SOC 2 Type II standard.
GDPR
Built for the EU with full GDPR data-subject rights.
CCPA
California opt-out, do-not-sell, plus DSAR handling.
ISO 27001
Information security held to the ISO 27001 standard.
ISO 42001
AI governance aligned to the new ISO 42001 standard.
Free resource
The 9-Point Email Verification Checklist
A 17-page field guide: every verification check explained, the five hidden mistakes that kill deliverability, and a one-page audit you can run this afternoon. Free PDF.
Common questions
Email verification, answered straight
The questions teams ask before trusting us with a list, answered with the real numbers and the real limits.
What does email verification actually check?
Nine things per address: syntax and format against RFC 5321 and 5322, domain existence with MX records, an SMTP handshake that pings the specific mailbox, disposable-domain match, role-address detection, catch-all detection, AI-confidence scoring on catch-all addresses, domain age, and email authentication records (SPF, DKIM, DMARC). You can watch all nine run on a single address in the free email checker.
How accurate is Verifox email verification?
99.99% on a 1,000-address benchmark list, self-measured, with catch-all domains included in the benchmark rather than excluded from it.
The free widget on this page, the single email verifier, and the paid API all run the exact same engine. Free tiers cap volume, never accuracy.
How fast can I verify a large email list?
Bulk verification runs at roughly 10,000 emails per minute on the standard tier, so a 50,000-address list finishes in about five minutes. A single check returns in around 380ms median, sub-50ms when cached. For pasting a batch by hand, the multiple email checker handles small lists without an upload.
What is a catch-all domain and why does it break most verifiers?
A catch-all domain accepts mail for every address, real or invented, so the standard SMTP question “does this mailbox exist?” always comes back yes. Most tools shrug and mark the whole domain “unknown.”
That gap matters: 20 to 40% of B2B lists fail at catch-all domains. Verifox scores those addresses individually with AI-confidence analysis. Test one yourself on the catch-all email checker.
Do you store or sell the emails I verify?
No. Every address is processed in memory and discarded the moment its verdict returns. Nothing is logged, retained, or sold, and the platform is SOC 2 Type II audited. The privacy policy and security page document exactly what we touch and what we never do.
How much email verification can I do for free?
Three free layers. The widget on this page and the free email checker allow 4 checks per day with no account at all.
Signing up adds 1,000 free credits, or 2,500 if you register with a work address. No card required, and paid credits on every plan never expire.
Can I verify email addresses in real time through an API?
Yes. The REST API returns a full nine-check verdict in about 380ms median, fast enough to validate signups before the form submits. Endpoints, SDKs, and a sandbox live in the API docs. AI agents can skip the glue code entirely with the native MCP server, and FoxGuard drops the same checks onto any web form as a widget.
How often should I re-verify my email list?
Before every major campaign, and monthly for lists you mail regularly. Addresses decay constantly as people change jobs and domains lapse, so a list verified a quarter ago is not a verified list. Between cleans, run sends through the email bounce checker and re-verify the moment bounces creep above 1%.
What is the difference between email verification and email validation?
In practice the words get used interchangeably, but validation often means format-only checks: does the string look like an email address. Verification goes further and talks to the receiving mail server to confirm the mailbox exists and can accept mail. Verifox does both on every check. Compare the free email validator and the email verifier to see the same engine framed for each job.
Why do verified lists still get a few bounces?
Because mailboxes die between the day you verify and the day you send. Greylisting, full inboxes, and sudden domain changes can also bounce a genuinely valid address. Expect a residual rate near 1% on a freshly cleaned list, not zero. If bounces stay high after cleaning, the problem is usually your sending domain's reputation; run it through the email blacklist check to rule that out.
Start free
Verify your first 1,000 emails free
Create a free account and 1,000 credits land before your list finishes uploading, 2,500 if you sign up with a work address. No card. Upload a CSV, paste addresses, or call the API; a 10,000-address list finishes in about a minute.
Get 1,000 free creditsNo credit card required
