Paste the address
Drop any email into the pill — Gmail, Outlook, custom domains, or role aliases like info@ and sales@. Verify one address free right now, or upload a CSV to check a whole list once you sign up.
Continuous Deliverability Watch
Deliverability Monitoring Catches Decay Before Bounces
The mail monitor for email deliverability that re-runs MX, SMTP, mailbox, and SPF, DKIM, DMARC checks on every address. Same 9-point engine as our paid API.
Free to try. No signup, no card.
Baseline, sweep, repeat
How email deliverability monitoring works
No signup, no card. Paste any address, get a deliverable or bounce verdict in seconds, and repeat on a cadence to catch list decay early.
Run the 9-check engine
Nine checks fire in parallel: syntax, DNS, and MX records, a live SMTP handshake, catch-all and disposable detection, role and domain-age signals, mailbox state, and email authentication, then you get the full verdict.
Read the verdict
Every address comes back valid, invalid, or risky, with the format, address type, server status, and mailbox status called out on the page. The API returns the same verdict with a 0-100 confidence score and the full per-check breakdown.
The plain-English version
What Email Deliverability Services Monitor
Same nine checks as the one-off test, run on a schedule so decay never builds up silently.
Deliverability monitoring is the address side of list health, run on a schedule. Most monitoring tools cover blacklist status and sending reputation — the right first half, but they skip the addresses. Mailboxes decay constantly: people change jobs, inboxes get retired, and 20 to 40% of B2B lists quietly fail at catch-all domains that accept every probe. The nine-check sweep catches those before they bounce.
The 9-point engine
Nine checks, one verdict
The same nine-check engine our paid email verification API runs. Every email, every verification, every time.
- 01
Syntax
Every address runs a full RFC 5321 and RFC 5322 compliance pass before a single network call goes out. The engine catches what visual scanning misses, the double dot in
alice@verifox..ai, the trailing period, the IDN homograph that looks valid but resolves to a different domain.Bundled typo suggestions let your form offer “did you mean alice@gmail.com?” instead of rejecting silently.
/dashboard
- 02
Domain & MX
Once syntax passes, the engine resolves the domain. We confirm the DNS records exist, fetch the MX record priority list in order, and verify at least one mail-exchange server is actively accepting connections right now.
Misspelled domains like
gmial.com, expired domains, and parked-for-sale domains all fail this gate before the engine wastes a single SMTP roundtrip./dashboard
- 03
SMTP handshake
The engine opens a TCP connection on port 25, performs the EHLO handshake, then negotiates
MAIL FROMandRCPT TO. Every server response code (220, 250, 550, 552) is parsed deterministically against the IANA enhanced-status registry.This is the moment a mailbox proves it actually exists. No third-party guesses, no statistical heuristics, just the receiving server's own answer.
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- 04
Catch-all detection
Some domains accept every email regardless of whether the mailbox exists, a setup known as a catch-all configuration. The engine sends a deterministic probe to a deliberately fake address (
zzz9k7q@domain.com); if the server returns the same 250 OK it returned for the real address, the domain is catch-all.The verdict isn't dropped, it's flagged RISKY so you know the deliverability signal is degraded.
/dashboard
- 05
Disposable
The engine maintains a curated registry of 10,247 disposable email providers, including Mailinator, Guerrilla Mail, 10MinuteMail, Tempmail, and the long tail of regional clones.
Any address matching the blocklist is flagged INVALID. Deliverability to a mailbox that exists for 10 minutes and is never checked is functionally zero, regardless of whether the SMTP handshake passes.
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- 06
Role address
info@,support@,no-reply@,admin@,billing@. These are shared inboxes, not individuals.The engine extracts the local-part of every address, matches it against the known role-prefix registry, and tags the result with a reduced engagement score.
You don't drop them automatically. The verdict flags them as roles so you can decide.
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- 07
Domain age
Fresh-spam domains registered hours ago are the single biggest source of inbound abuse. The engine queries WHOIS and RDAP for every unique domain, extracts the registration date, and flags anything under 30 days old with a “fresh” warning.
Domains aged 5+ years pick up a corresponding trust signal. The same heuristic spam filters have been using since the early 2000s, ported into the verdict.
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- 08
Email authentication
SPF, DKIM, and DMARC together prove the sender is authorised to send from that domain.
The engine reads each policy via DNS, validates SPF includes recursively, scans six common DKIM selectors, and confirms DMARC alignment with the
From:header.A failing DMARC policy means the sender can be spoofed, so the verdict warns you before you reply.
/dashboard
- 09
Mailbox state
Beyond “exists vs doesn't exist”, the engine extracts the precise mailbox state from the SMTP server's response. Full inbox (552 / 522 quota), disabled mailbox (550 5.1.1), out-of-office autoresponder, frozen account.
Each state maps to a specific retry policy. Full inbox retries in 6 hours. Disabled drops permanently. The verdict tells you which bucket the bounce belongs in so your retry logic doesn't waste cycles.
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What it tells you
What an MX lookup reveals about a domain
An MX lookup is a read-only window into how a domain receives email. In one query you learn who runs the mail, how it routes, and whether it can receive at all.
Verification engine
9checks on every
checks on every
address
The same DNS resolution the Verifox verification engine runs first on every address it checks.
Who runs the mail
The MX hosts name the provider — Google Workspace, Microsoft 365, Proofpoint, or a self-hosted server.
Routing and priority
Records return lowest-number-first, so you read the primary server and its fallbacks straight away.
A deliverability signal
No MX record, or a broken one, means mail bounces before it is ever sent.
The first deliverability step
An MX lookup starts the story; verifying the address confirms the mailbox itself is real.
Verify the mailbox itself
An MX lookup is only the first step. Verifying the address confirms the mailbox is real and deliverable.
Provider at a glance
The single most useful thing a mail exchanger lookup tells you — who to talk to about mail.
How we stack up
Verifox vs the
alternatives
Same nine-check pipeline, a 0-100 catch-all confidence score, credits that never expire, and an MCP server no competitor offers. Head-to-head with the two providers our buyers shortlist.
★ The complete monitorVerifox
NeverBounceYes
ZeroBounceNever
NeverBounce1,000 / monthly
ZeroBounce100 / monthly
NeverBounce
ZeroBounce
NeverBounceFlagged only
ZeroBounceAI scoring
NeverBounce
ZeroBounce
NeverBounce
ZeroBounce
NeverBounce
ZeroBounce
NeverBounce
ZeroBounce
Pricing
Pay once, or not at all
Most tools reset your balance every month. Verifox sells credits that sit in your account until you spend them.
FreeProve it on your own list before you spend anything.$0
forever
1,000credits on signup
No card required
2,500 with a work email
Free includes
- All 9 checks included
- Full API and bulk CSV
- Catch-all confidence scoring
- No card required
Most popular
Credit packsBuy once, spend whenever. Slide to price your list.$59
one time
10,000credits
$0.0059 eachSAVE 34%
Everything in Free, plus
- Credits never expire
- Verify or find from one pool
- Up to 79% off at volume
- No contract, no minimum
Verifox ONECredits land monthly and stack on your balance.$79
per month
15,000credits a month
$0.0053 each
Unused credits roll over
Everything in packs, plus
- Unused credits roll over
- Our lowest per-email rate
- Full REST API access
- Cancel anytime
One credit verifies one address; a find costs 10, a company search 100 and an email reveal 50. All prices in USD, secure checkout via Dodo Payments.
Prices are before tax. Any VAT, GST or sales tax your country charges is added at checkout. Buying as a business? Enter your VAT or GST number there.
Your data stays yours
The addresses you submit are used only to run your verification. They are never sold, and nobody on your list hears from us.
Never sold
The addresses you submit are never sold or shared.
No email sent
We ask the mail server. Not one message is sent.
GDPR
Full GDPR data-subject rights for everyone in the EU and UK.
CCPA
California opt-out, do not sell and DSAR handling.
Free field manual
The Dead List
An investigation into the money leaking out of your list - and the nine checks that decide whether your email is read, or never arrives at all.
Get the free manual
57 pages, free PDF, no signup
Common questions
Deliverability monitoring, answered.
Common questions about deliverability monitoring: what changes between checks, how often to run sweeps, and where monitoring fits alongside one-time verification.
What is email deliverability monitoring?
Email deliverability monitoring means re-checking, on a schedule, the signals that decide whether your mail gets accepted: live mailboxes, valid MX records, a passing SMTP handshake, and SPF, DKIM, and DMARC authentication. A one-time list scrub answers those questions for a single day; monitoring keeps answering them as mailboxes die, DNS records change, and forms collect new junk.
Verifox runs nine checks per address on every pass, the same pipeline behind our email verification service, so a monitoring sweep is a full verification, not a cached lookup.
Is Verifox a mail monitor for email deliverability?
For the address and authentication side, yes. Classic mail monitor services watch your sending domain: blacklist listings and inbox placement panels. Verifox monitors what those services assume is already fine, whether the mailboxes on your list still exist and whether your SPF, DKIM, and DMARC records still pass.
The two halves complete each other. Run your sweeps here, then cover the domain-reputation side with the email blacklist check and the domain reputation checker.
Is the deliverability monitoring free to start?
Yes. The scanner on this page gives you 4 checks per day with no account and no card. That is enough to spot-check your own address and your highest-value contacts daily.
Sign up free and 1,000 credits land once you verify your email, 2,500 if you register with a work address. From there credits are pay-as-you-go with volume discounts on larger packs.
Which deliverability signals does each monitoring pass cover?
Every address goes through nine checks in parallel:
- Syntax and format (RFC 5321 / 5322)
- Domain existence and MX records
- SMTP handshake and mailbox ping
- Disposable-domain match
- Role-address detection
- Catch-all detection, with AI-confidence scoring
- Domain age
- SPF, DKIM, and DMARC authentication
The authentication leg is the one most list tools skip entirely. If you only need that piece, the standalone DMARC, DKIM and SPF check runs it on its own.
How often should I monitor my list's deliverability?
Before every meaningful send, and at least monthly for any list you mail regularly. Addresses decay constantly: people change jobs, companies migrate domains, and inboxes get retired without notice. A list that verified clean a quarter ago is a different list today.
The expensive failure mode hides at catch-all domains, where 20 to 40% of B2B email lists actually fail. Those domains accept every probe a basic checker sends, so only the catch-all resolution with AI scoring catches the dead ones between sends.
Can I automate deliverability monitoring with the API or an AI agent?
Yes, that is how most teams run it. A scheduled job hits the REST API, sweeps the list, and routes anything that flips to undeliverable back into your CRM.
AI agents get the same engine with zero glue code through the native MCP server: point Claude, Cursor, or a custom agent at the MCP URL and the monitoring tools are wired.
Does monitoring cover my DNS and authentication records too?
Yes. The ninth check validates SPF, DKIM, and DMARC on the sending domain, and the MX leg confirms mail routing still resolves. DNS edits are the classic silent killer: one rewritten TXT record turns a passing SPF into a SoftFail, and nothing tells you until open rates sag.
For deeper single-purpose digging, the MX lookup, DKIM tester, and SMTP test each isolate one layer of the same stack.
What happens to the addresses I run through the monitor?
They are used only to run the verification and show you the result. Verifox never sells the addresses you monitor, which matters when the list you are sweeping is your customer base.
Verifox is GDPR and CCPA compliant; our security overview has the details, and the privacy policy spells out exactly how your data is handled.
What does ongoing monitoring cost at volume?
One credit per address per pass, and credits never expire, so a monthly cadence wastes nothing if a sweep slips a few weeks. Volume rates step down as usage grows; exact numbers are on the pricing page.
Custom SLAs are available on annual Volume contracts, with live status at status.verifox.ai.
How is monitoring different from a one-time deliverability test?
Same engine, different posture. A one-time deliverability test answers “is this address good right now?” Monitoring asks that question again next week, because the answer changes. The verdicts themselves are identical: deliverable, undeliverable, or risky, with a confidence score and a per-check breakdown.
If you want a single composite grade for an address instead of a recurring sweep, the email health checker frames the same nine checks as a one-shot report card.