Free SMTP Tester & Mail Server Checker

Is your SMTP actually delivering?

Send a real message to our mailbox the same way you'd send to a subscriber. We'll show you whether it arrived — and where.

Forward a test email here:
sprinting-frog-7937@in.mailtester.ai

Report in ~30s · one-time address · we never see your list
Not ready? See a sample report first.

Example result

mailtester.ai/report/live
sara@lisbonletters.beehiiv.com
received 14s ago · AI classifier verdict (no real send)

"This week: 5 things I'm reading after Lisbon Web Summit ☀️"

Deliverability 62/100
Verdict Risky — don't send yet

Where it lands
Primary 38% · Promotions 41% · Spam 21%

3 quick fixes · first: subject emoji trips Gmail's promo filter +2 more

Free SMTP Tester & Mail Server Checker

What does an SMTP test check?

It confirms your mail server accepts connections, authenticates correctly, and can actually deliver mail — the plumbing that has to work before deliverability matters.

Is this the same as checking deliverability?

Not quite. SMTP testing checks that your server can send; deliverability checks whether what you send lands in the inbox. Mailtester focuses on the second — where your campaign actually ends up.

How do I test my SMTP setup?

Forward an email through your server to your Mailtester address. We read the delivery path from the real message and flag any connectivity or authentication problems.

Built in the EU · GDPR by default
6,500+ emails tested
AI-classified across real Gmail, Outlook, and Yahoo inboxes.
Free · €0 for unlimited scoring. €9.99 for AI deep-dives.

How it works

Three steps. About thirty seconds, end to end.

01~10 sec

You forward it.
Paste the mailbox above into the test-send field in Beehiiv, Kit, Substack, Mailchimp — or your own inbox. Hit go. We never see your subscriber list.

02~10 sec

We actually open it.
In real Gmail, real Outlook, real Yahoo. We watch where your email lands — Primary, Promotions, or Spam — using the same filters that decide whether your campaign worked.

03~10 sec

You get a report.
Plain English. Three things to change, in priority order. Unlock the bundle and we generate a subject, body, and CTA rewrite in your voice — paste them back into your campaign before lunch.

Two different tests. Most people mix them up.

If you've ever searched "email tester," half the results check whether the address is valid. We do the other thing — whether the email itself will reach the inbox once you press send.

Address validity
Does this address exist?
You upload a CSV of subscribers. The tool tells you which addresses bounce. Great for cleaning a stale list before a re-engagement send.

That's us

Inbox placement
Will Gmail actually show it?
You forward one email — newsletter, launch, client note — to a one-time mailbox. We open it in real Gmail, Outlook, and Yahoo and tell you which tab it landed in, plus what to rewrite before you send it to your list.

Use both, actually— verify the list, then score the send.

Other free checks worth two minutes

Pricing

Free to score. Pay only for the AI deep-dive.

Forward any email and get the score — free and unlimited. Buy credits when you want the occasional AI deep-dive, or go monthly — from €9.99 — if you send regularly. Cancel from the same screen you upgrade on.

Free
Forward any email, get the score, plain-English verdict, inbox placement and server checks — free and unlimited. No card needed.

€0
Start free

Credits
About 5 AI deep-dives. Top up only when you need them — credits never expire.

€4.99 one-time · 499 credits
Buy credits

Starter
1,100 credits a month, about 11 AI deep-dives. Cancel anytime.

€9.99/ mo
Subscribe

Best for weekly senders

Pro
A standing watch on your sender: 2,500 credits a month, about 25 AI deep-dives. Re-check every weekly send.

€19/ mo
Subscribe

Send your next one to the inbox.

Takes less time than picking a hero photo. Free, and no card at any point.

sprinting-frog-7937@in.mailtester.ai

Or send me a sample report first.