Clean your whole list before the next send
Drag in a file with five hundred rows or five million. MailTester dedupes, runs all twelve verification engines on every address, and hands back exactly the segments you want to keep.
Your list is quietly rotting
Email lists decay at roughly 2% per month — people change jobs, abandon inboxes, and let domains expire. Do nothing for a year and about a quarter of your list is dead weight you're still paying to store and send to.
You pay your ESP for ghosts
Most ESPs charge by list size. Every dead address on a 50,000-row list inflates the invoice month after month while contributing exactly zero opens.
One dirty send can poison weeks
Blast an aged segment and the bounce spike tells Gmail you don't maintain your list. The reputation damage outlives the campaign — your clean sends suffer too.
Spam traps hide in old segments
Abandoned addresses get recycled into traps by mailbox providers. They never bounce and never complain — they just silently report you to blocklists.
Twelve engines run on every single row
Bulk doesn't mean shallow. Each address in your file gets the full treatment: syntax and typo checks, MX resolution, a live SMTP conversation, plus screening against spam-trap, disposable and complainer databases. Greylisted servers are retried until they give a real answer.
- Live SMTP verification for every address — not sampling, not guessing
- Spam traps and serial complainers flagged from continuously updated databases
- Anti-greylisting retries convert “unknowns” into definitive verdicts
Deduplication and syntax filtering — free, before billing starts
Files accumulate junk: exact duplicates, case variants, rows with broken formatting. MailTester normalizes and merges them before verification begins, and none of it consumes credits. You pay only for unique, structurally valid addresses that reach the engine.
- Exact and normalized duplicates merged automatically
- Syntax-invalid rows filtered out at no charge
- Transparent count of what was removed and why, before you spend a credit
Download exactly the segment you need
The output isn't one verdict-stamped file you still have to slice in a spreadsheet. Deliverable, risky and undeliverable come as separate, ready-to-import downloads — or build a custom filter on score, domain type or any flag, and export just that slice as CSV or XLSX.
- One-click downloads per segment: deliverable, risky, undeliverable
- Custom filters on score, role, free-provider, disposable and more
- Push clean segments straight back to your ESP via integrations
Three steps, no learning curve
- 01
Upload or sync
Drop a CSV/XLSX, paste addresses, or connect your ESP and pick a list. Column mapping is automatic.
- 02
We verify every row
Dedupe, syntax, MX, live SMTP, spam traps, disposables, complainers — all twelve engines, every address, with live progress.
- 03
Download your segments
Deliverable, risky, undeliverable — separately or filtered however you like, with the score for every row.
- 5M
- rows per upload
- ~25%
- of a typical list removed
- <30min
- for a 100K-row list
- $0.0003
- per email at volume
Built for serious list sizes
Fast at any scale
Millions of rows verify in minutes to hours, not days — with live progress and an email when results are ready.
Free deduplication
Duplicates and syntax-invalid rows are removed before billing — you never pay to check the same person twice.
Spam trap removal
Known and suspected traps are flagged before they can torch your reputation with the blocklist operators.
Complainers database
Addresses with a history of marking mail as spam are flagged from our continuously updated list.
Segmented downloads
Deliverable-only for the next campaign, risky-only for re-permission, or any custom slice — CSV or XLSX.
Team accounts & shared credits
One credit pool for the whole team, with per-member activity visible to admins. Built for agencies.
When teams reach for bulk cleaning
Before a big campaign
Product launches and Black Friday sends are exactly when a bounce spike hurts most. Clean first.
Reviving an old list
A segment untouched for six months is a minefield. Verify it before the win-back campaign, not after.
Agencies with client lists
Clean every client's list from one account and one credit pool, with activity tracked per member.
Migrating ESPs
New ESPs judge you by your first sends. Arrive with a clean list and start with a clean reputation.
We were looking for a mail validation service that can handle a large volume of emails and return accurate results. Now MailTester.com is our go-to solution.
Mailtester is awesome. We have big lists here with us and we keep them clean with MailTester.com. It never disappoints.
What does bulk email verification actually do?
Bulk verification runs every address in a file through the same gauntlet a single check uses — syntax validation, DNS and MX lookups, a live SMTP conversation with the receiving server, and screening against disposable, spam-trap and complainer databases. The difference is orchestration: thousands of checks run in parallel, greylisted servers are queued and retried, and results are aggregated into segments you can act on.
The output for each row is a verdict (deliverable, risky, undeliverable), a 0–100 quality score, and the individual signals behind it — role account, free provider, disposable, catch-all domain. That detail matters: a risky catch-all and a risky disposable deserve different treatment, and a flat valid/invalid answer hides the difference.
How often should you clean a list?
Active lists: quarterly. Addresses decay at roughly 2% per month even on a healthy list, so a quarterly pass keeps your bounce rate comfortably under the thresholds mailbox providers punish. Any list that hasn't been mailed in three months or more: verify before the next send, no exceptions — that's where bounce-rate disasters come from.
The other moment that matters is the high-stakes send: a launch, a seasonal campaign, a re-engagement blast. Those are precisely the campaigns where a bounce spike does the most damage, and precisely when a 30-minute cleaning pass is the cheapest insurance available.
Is it safe to upload my list?
Your list is your asset, and we treat it that way. Files are encrypted in transit and at rest, processed solely to produce your verification results, never shared, sold or used to build anything of ours — and you can delete them permanently from your dashboard at any time. A Data Processing Agreement is available to every customer; data handling is documented in our privacy policy.
Pay only for what you verify
Credits from $19, volume rates down to $0.0003 per email — and they never expire. Subscriptions bundle inbox testing and monitoring.
How many emails do you need to verify?
50,000credits
$79
$0.0016 per email
Common questions
About a quarter of the average list is dead weight.
Upload yours and see the breakdown — your first 100 verifications are free.