Email verification, done properly
Every list decays — about 2% of addresses go bad every month. Verification finds the dead ones before mailbox providers do, protecting your deliverability and the money you spend on every send.
The cost of an unverified list
Skipping verification doesn't save money — it just moves the cost somewhere less visible: your ESP invoice, your sender reputation, and the revenue your campaigns quietly stop producing.
Inflated ESP bills
ESPs charge by list size. Carrying a quarter of dead weight means paying a quarter more, every month, for subscribers who can't open anything.
Spam-folder drift
High bounce rates tell Gmail and Outlook you don't maintain your list. Their response is silent: more of your mail goes to spam, including to engaged subscribers.
Metrics you can't trust
Open and click rates calculated over a denominator full of dead mailboxes understate your real performance — and hide the trends that matter.
What verification actually checks
Proper verification is layered. Syntax validation catches malformed addresses and typos. DNS checks confirm the domain exists and publishes MX records. A live SMTP conversation asks the receiving server whether the specific mailbox accepts mail. And database screening flags disposables, spam traps, complainers and role accounts.
- Live SMTP mailbox check on every address — the part most tools skip
- Spam-trap, disposable and complainer screening from updated databases
- Typo correction that rescues subscribers instead of discarding them
Risk scoring, because reality has shades
Catch-all domains accept mail for any address; greylisting servers stall first attempts; role accounts exist but complain. Binary valid/invalid tools either guess or give up on these. MailTester scores every address 0–100 and labels the risk precisely, so your send/suppress line is a policy you choose.
- Catch-alls flagged with a usable risk score, never guessed valid
- Greylisting resolved with correctly timed retries
- Role, free-provider and disposable flags on every result
From verdicts to a sendable list
Verification is only useful if it changes what you send. Results come as segments — deliverable, risky, undeliverable — each downloadable separately or pushed straight back to your ESP. Keep the deliverables, re-permission the risky, and let the dead addresses go.
- Segmented downloads ready to import anywhere
- Two-way ESP sync via integrations — no CSV gymnastics
- Score on every row for custom thresholds
Three steps, no learning curve
- 01
Syntax & domain checks
Malformed addresses, typo domains, and domains without mail servers are eliminated first — instantly and free.
- 02
Live mailbox verification
A real SMTP conversation per address, with anti-greylisting retries, confirms whether each specific mailbox accepts mail.
- 03
Risk scoring & segmentation
Spam traps, disposables, role accounts and catch-alls are scored 0–100 so you decide what to keep, re-confirm, or drop.
- 99%
- verification accuracy
- <1%
- achievable bounce rate
- ~2%
- of any list decays per month
- 100
- free checks to start
What a verified list buys you
Bounce rate under 1%
Removing undeliverable addresses keeps your bounce rate below the thresholds Gmail and Outlook punish.
Protected sender reputation
Spam traps, complainers and disposables — the addresses that silently poison your domain — get caught first.
Smaller ESP invoice
Cleaning the average list cuts it by roughly a quarter — same reach, smaller bill, every month after.
Honest metrics
Open and click rates calculated against real humans, not a denominator full of dead mailboxes.
Better inbox placement
Lower bounces and fewer complaints feed directly into how providers rate you — and where they file your mail.
Compounding returns
Verify at signup and quarterly, and list quality stops decaying — the cleanup becomes maintenance.
Verification across the lifecycle
At collection
API checks on signup forms stop typos and disposables from ever entering your database.
In bulk
Quarterly cleans for active lists; mandatory cleans for anything untouched for 3+ months.
Before the big send
Launches and seasonal campaigns are when a bounce spike hurts most — verify first.
During migrations
Arriving at a new ESP with a clean list means starting with a clean reputation.
When I signed up for MailTester.com, I was a bit skeptical at first. How much difference can it make for a relatively smaller company like us? Answer: a lot. We didn't change our email strategy much, still our email open rate has increased like 3-4%. I recommend MailTester.com.
We are a small startup and can't afford to spend hundreds of dollars every month on email verification. MailTester.com's flexible pricing plan works for us.
What is email verification?
Email verification is the process of confirming that an email address can actually receive mail — before you send anything to it. A proper verification combines several checks: the address format, the domain's DNS and MX records, a live SMTP conversation with the receiving server, and screening against databases of disposable providers, spam traps and chronic complainers.
The output is more than valid/invalid. Modern verification assigns each address a risk profile: a corporate mailbox that answered the SMTP check is a different asset than a catch-all domain that accepts everything, even though neither will hard-bounce today.
When should you verify?
At collection: wire verification into your signup forms via API, so typos and disposables never enter your database. In bulk: clean any list that has not been mailed in the last three months, and re-clean active lists quarterly — addresses decay at roughly 2% per month.
Before a high-stakes send is the moment that matters most: a product launch, a Black Friday campaign, a re-engagement blast to old contacts. Those are exactly the sends where a bounce spike does the most reputation damage.
Verification vs. validation vs. deliverability
The terms get used loosely. Validation often refers to format and syntax checking only — the cheap part. Verification includes the live mailbox check that actually predicts bounces. Deliverability is the bigger question of whether mail from your domain reaches the inbox at all, which depends on reputation, authentication and content on top of list quality.
MailTester covers the full stack: verification (single, bulk and API) keeps the list clean, and the inbox placement tester with blacklist monitoring covers the deliverability half. One platform, both halves of the problem.
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
Find out what 99% accuracy looks like on your list.
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