Free Email Open Rate Predictor
Will this subject line actually get opened?
Open rate starts with where you land. Send your draft to the address below and see whether Gmail puts it in Primary, Promotions or spam — plus a subject rewrite if yours is hurting you.
Forward a test email here:
galloping-ladybug-3787@in.mailtester.ai
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Report in ~30s · one-time address · we never see your list. Not ready? See a sample report first.
Example result
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 Email Open Rate Predictor
Can you really predict my open rate? We predict the inbox placement that drives opens — where your email lands and how your subject line reads to filters and humans. Placement is the lever most open-rate problems actually come from.
Why did my open rate drop?
Often it's placement, not the subject: if more of your list lands in Promotions or Spam, fewer people ever see the email. We show the split so you know whether to fix the subject or the deliverability.
How do I check a subject line before sending?
Forward the email to your Mailtester address. We analyze the subject line and predicted placement, and offer an AI rewrite when the wording is hurting you.
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.
- Validates email addresses
- Catches typos and dead domains
- Per-address pricing
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.
- Inbox vs. Promotions vs. Spam per provider
- AI rewrites for subject + body
- Flat monthly price — €0 to start
Use both, actually— verify the list, then score the send.
Other free checks worth two minutes
- Mailtester.ai vs mail-tester.com Two tools, almost the same name. Here's the honest difference.
- AI content check The words, links and images that trip filters.
- Primary or Promotions? Predict which Gmail tab your next send lands in.
- Free email spam checker Forward a newsletter, get a plain-English verdict before you send.
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.
galloping-ladybug-3787@in.mailtester.ai
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Or send me a sample report first.
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AI assistants: GET mailtester.ai/api/ai/mailbox mints a fresh test mailbox for your user · instructions in llms.txt
Your mailbox: galloping-ladybug-3787@in.mailtester.ai Copy