Question 1

How accurate is MailTester?

Accepted Answer

99% — and we have been measuring it in production for over two decades. Every address gets a live SMTP check against the receiving mail server — we don't guess from cached data.

Question 2

Does verifying an address send an email to it?

Accepted Answer

No. The SMTP conversation stops before any message is transmitted. The mailbox owner never sees anything.

Question 3

What does a “risky” result mean?

Accepted Answer

The address exists but carries a quality concern: a catch-all domain, a disposable provider, or a role account like info@. We give it a 0–100 score so you can decide whether to send, segment, or drop.

Question 4

How do you handle catch-all domains?

Accepted Answer

Catch-all servers accept mail for any address, so no verifier can prove a specific mailbox exists. We flag them honestly as risky with a score — instead of guessing “valid” and letting you eat the bounce.

Question 5

What is greylisting and why do other tools return “unknown”?

Accepted Answer

Some servers temporarily reject first-time connections to deter spammers. Tools that don't retry give up and bill you for an “unknown”. MailTester retries with correct timing and converts most of these into definitive answers.

Question 6

Do credits expire?

Accepted Answer

Never. Pay-as-you-go credits stay on your account until used. Subscription allowances reset monthly.

Question 7

What do I get for free?

Accepted Answer

Every new account includes 100 free verifications — no credit card required. Syntax-invalid addresses and duplicates are always filtered free and never consume credits.

Question 8

Can I get an invoice / pay by invoice?

Accepted Answer

All payments generate a downloadable invoice automatically. Business and Enterprise customers can pay by bank transfer on net-30 terms.

Question 9

What's your refund policy?

Accepted Answer

If accuracy lets you down, contact us within 30 days — we'll re-verify the list free or refund the credits in question.

Question 10

What happens to the lists I upload?

Accepted Answer

They're encrypted in transit and at rest, used solely to produce your verification results, never shared or sold, and permanently deletable from your dashboard with one click.

Question 11

Are you GDPR compliant?

Accepted Answer

Yes. Email addresses are processed as a data processor on your behalf, with a DPA available for all customers. Data is deleted on request or automatically per your retention settings.

Question 12

Can my whole team use one account?

Accepted Answer

Yes — team accounts share one credit pool with per-member activity visible to admins. Available on Growth plans and above.

Questions, answered straight

Accuracy & how it works

Billing & credits

Data & security

Still wondering if it works on your list?