The Mails.so Insider’s Guide
Everything we know about Mails.so in one document: what it costs, its grades, getting a refund, getting help and what else to look at. Read it here, or keep a copy.
Mails.so
The Insider’s Guide
Email validation API and list checker with flat monthly plans
Every plan, grade, refund rule and rival among email verification and deliverability tools, read from Mails.so’s own pages.
Made by Mails, Inc. · checked Nov 13, 2026 · toolgpa.com
Contents
- 01WelcomeWhat it is, who it suits, its grades and the ten things to know first
- 02What it costsEvery plan, the free plan, ways to pay less and how prices have moved
- 03What it doesIts main features, where it runs, what it works with and who makes it
- 04Where it standsIts grades against its category, and whether to keep it or make your own
- 05The alternativesThe tools it is most often weighed against, side by side
- 06Quick answersThe questions people ask about it, each answered in a line or two
- 07About ToolGPAWho made this guide, what else is on the site, and how to cite it
ToolGPA put this guide together from Mails.so’s own pages, its app-store listings and our grades. Every fact in it is on Mails.so’s page too, where it is kept up to date. Checked Nov 13, 2026.
Part 01 · Overview
Welcome
What it is, who it suits, its grades and the ten things to know first
2.2
GPA, above 23 of the 61 other email verification and deliverability tools we grade
Mails.so is an email validation service with a web checker, list upload and an API. Paid plans are monthly and all include API access, list validation, an email finder and Mailchimp and HubSpot integrations. The pricing section sits on its homepage and is shown in euros.
To get you started, here are 9 things to know about Mails.so, taken from its own pages and our grades.
- 1
Best for an email validation API with flat monthly plans
Mails.so validates addresses by list or API on flat monthly plans, from €48 for 10,000.
- 2
Paid plans start at about $53.63 a month
As its pricing page puts it: €48 per month for 10,000 validations, shown in euros.
- 3
You can try it first
50 free credits on sign-up, no credit card required
- 4
It runs on Web
Web.
- 5
List validation
Upload a list to check its addresses, or paste single addresses into the checker on the homepage.
- 6
Validation API
Every paid plan includes API access, for checking addresses at signup or inside other software.
- 7
Email finder
An email finder is included on all three paid plans.
- 8
A 2.2 GPA, above 23 of 61
That is against the other email verification and deliverability tools we grade, on value, the free plan, features, ease of use and platforms.
- 9
Keep it
Nothing Mails.so does is plain enough to make in a weekend. The 2 things listed below take a company.
Mails.so at a glance
- Pricing
- Free trial, from €48 per month for 10,000 validations, shown in euros
- Free plan
- No
- Free trial
- 50 free credits on sign-up, no credit card required
- Runs on
- Web
- Made by
- Mails, Inc.
- Category
- Email Verification & Deliverability
- Our grade
- 2.2 GPA, fair
The report card
Best for an email validation API with flat monthly plans
Mails.so validates addresses by list or API on flat monthly plans, from €48 for 10,000. The first month is 90% off and then renews at full price, the free allowance is a one-time 50 credits, and we only saw euro prices.
| Subject | Grade | Comment |
|---|---|---|
| Value for money | C | €48 a month for 10,000 validations, which is near the category's $49 dearer quarter once converted. The dollar price is unconfirmed. |
| Free plan and trial | C | 50 free credits on sign-up with no card, once. No monthly free plan. |
| Features | C | List validation, an API and an email finder. Only the three paid plans are listed, with no pay-as-you-go pack. |
| Ease of use | C | No store rating on record. You upload lists or use the API. |
| Platforms and integrations | B | Web and API with Mailchimp and HubSpot links. No apps. |
An A is worth 4 points, a B 3, a C 2, a D 1 and an F nothing. The GPA is the average of the five.
Who Mails.so is for
- Fits if you want a flat monthly price instead of buying packs
- Works for people who also want an email finder
Who it is not for
- Watch out: the 90% first-month discount lasts one month, then the plan renews in full
- Skip it if you want a free plan, since it's 50 credits once
- Pricey if you validate small amounts, as plans start at €48 a month
- Watch out: prices were read in euros and the dollar price is unconfirmed
Good to know
Good for
- Developers and teams wanting a predictable monthly validation fee
- Small lists, using the 50 free credits first
- High-volume senders considering the unlimited plan
Worth knowing
- Prices were read in euros; a US dollar view could not be read, so the dollar price is unconfirmed.
- The 90% first-month discount applies to the first month only; the plan then renews at full price.
- The free allowance is a one-time 50 credits, not a monthly free plan.
- Only the three paid plans were listed; there is no separate pay-as-you-go pack on the page.
Part 02 · Pricing
What it costs
Every plan, the free plan, ways to pay less and how prices have moved
~$53.63
A month to start
Mails.so is a paid product with a free trial, starting at €48 per month for 10,000 validations, shown in euros.
Pro
€48
per month for 10,000 validations
First month €4.80 (90% off). 5 concurrent validations; top-ups at €0.005 per validation.
Business
€98
per month for 50,000 validations
First month €9.80 (90% off). 5 concurrent validations; top-ups at €0.002 per validation.
Unlimited
€498
per month for unlimited validations
First month €49.80 (90% off). 10 concurrent validations.
Trying it first
50 free credits on sign-up, no credit card required
Read from mails.so on Nov 13, 2026.
Ways to pay less
Other savings
90% off the first month
The homepage shows each paid plan at 90% off for the first month, then at full price. No end date is shown.
Stated on mails.so
Part 03 · Features
What it does
Its main features, where it runs, what it works with and who makes it
1
Place it runs: Web
Email validation API and list checker with flat monthly plans. Here is what it does, as its own site describes it, and what it covers: public API, email verification.
List validation, an API and an email finder.
- List validation
- Upload a list to check its addresses, or paste single addresses into the checker on the homepage.
- Validation API
- Every paid plan includes API access, for checking addresses at signup or inside other software.
- Email finder
- An email finder is included on all three paid plans.
- Mailchimp and HubSpot integrations
- Listed on every paid plan for cleaning lists held in those platforms.
- Top-ups
- Extra validations can be bought at any time on Pro and Business at a stated per-validation rate.
Where it runs
- Web
What it works with
- Mailchimp
- HubSpot
Mails.so is made by Mails, Inc.
Part 04 · Standing
Where it stands
Its grades against its category, and whether to keep it or make your own
23/61
Other email verification and deliverability tools it is graded above
Mails.so's GPA of 2.2 is higher than 23 of the 61 other email verification and deliverability tools we grade, and level with 13.
It stands best on platforms and integrations (B, above 28 of 61) and worst on features (C, above 0).
Its paid plans start at about $53.63 a month, against a middle price of $21.50 for the category: 34 of the 43 others that charge start lower.
On features, ease of use and platforms it scores 2.3 out of 4. 8 tools score higher and cost less.
Each grade against the category
Every bar is all 62 email verification and deliverability tools we grade, cut by the letter each got. Mails.so’s own letter is outlined.
- CValue for moneyAbove 9 of 61
- CFree plan and trialAbove 9 of 61
- CFeaturesAbove 0 of 61
- CEase of useAbove 2 of 61
- BPlatforms and integrationsAbove 28 of 61
Price against what you get
Each dot is one of 45 email verification and deliverability tools. Further left costs less; higher up scores better on features, ease of use and platforms. Mails.so is the marked dot.
What paid plans start at, a month (each step along is roughly double) →
Keep it, or make your own?
Whether this is something you could build for yourself with an AI app builder, and what you would give up.
Keep it
Nothing Mails.so does is plain enough to make in a weekend. The 2 things listed below take a company.
It costs $643.51 a year.
What you could not
- Checking that an address exists without writing to it.
- It plugs into other products, Mailchimp and HubSpot among them, and has an API.
What this rests on. Mails.so’s listing: what it does, where it runs, what it plugs into and what it costs. It is a judgement about the kind of software this is. We have not built a replacement for it, and making your own means looking after it too. How we decide, and every tool’s verdict.
Part 05 · Alternatives
The alternatives
The tools it is most often weighed against, side by side
ZeroBounce, NeverBounce, Emailable, MillionVerifier and Reacher
The 5 tools Mails.so is most often weighed against, with where each one differs from it.
- 2.4GPA
ZeroBounce
Free plan · from $39 one-time
Email list verification with warm-up and DMARC monitoring in one plan.
- ZeroBounce has a free plan. Mails.so does not, though it has a free trial.
- Only ZeroBounce lists an iOS app.
- ZeroBounce also covers inbox warm-up and dMARC.
- 2.4GPA
NeverBounce
Free trial · from $8 one-time
Email list cleaning and real-time verification, now part of ZoomInfo.
- 2.4GPA
Emailable
Free trial · from $38 one-time
Email list verification with inbox reports and blacklist monitoring.
- 2.4GPA
MillionVerifier
Free trial · from $39 one-time
Low-cost bulk email verification with credits that never expire.
- 2.0GPA
Reacher
Free
Open-source email verification engine with an HTTP backend.
- Reacher has a free plan. Mails.so does not, though it has a free trial.
- Reacher is open source and self-hostable, according to its own site.
Part 06 · Questions
Quick answers
The questions people ask about it, each answered in a line or two
14
Questions, each answered in a line or two
The short version of everything above, for when you only need the answer. Each one is told in full in its part of the guide.
Is Mails.so free?
No, Mails.so is a paid product, but you can try it first. 50 free credits on sign-up, no credit card required.
How much does Mails.so cost?
Mails.so lists 3 plans. Pro: €48 per month for 10,000 validations.
What platforms does Mails.so work on?
Mails.so is available on Web.
Does Mails.so offer any discounts?
Mails.so publicly lists the following: 90% off the first month.
Does Mails.so have an Android app?
No Android app was listed when its pages were read on Nov 13, 2026. Mails.so is listed for Web.
Does Mails.so have an iPhone app?
No iPhone app was listed when its pages were read on Nov 13, 2026. Mails.so is listed for Web.
Is Mails.so open source?
Mails.so is not described as open source on its own site, as read on Nov 13, 2026.
Does Mails.so have an API?
Yes. Mails.so offers a public API, according to its own site.
What does Mails.so integrate with?
Mails.so's listing names Mailchimp and HubSpot. A listing names up to eight integrations, so it may connect to more.
Who makes Mails.so?
Mails.so is made by Mails, Inc.
What are the alternatives to Mails.so?
The closest alternatives to Mails.so in our directory are ZeroBounce, NeverBounce, Emailable, MillionVerifier and Reacher.
How does Mails.so compare with other email verification and deliverability tools?
Mails.so's GPA of 2.2 is higher than 23 of the 61 other email verification and deliverability tools we grade, and level with 13.
Is Mails.so good value for money?
ToolGPA grades Mails.so C for value for money. Its paid plans start at about $53.63 a month, against a middle price of $21.50 for the category: 34 of the 43 others that charge start lower.
Could I make my own version of Mails.so?
Nothing Mails.so does is plain enough to make in a weekend. The 2 things listed below take a company.
Where this guide comes from
The prices, plans, platforms and features were read from Mails.so’s own pages on Nov 13, 2026, and the grades were given on Nov 13, 2026. Graded from this listing, whose facts were read from Mails.so's own pages on 13 November 2026. Not based on using the product, and shorter than our full reviews.
Every tool we list gets five grades, A to F, each with its reason, and a GPA that averages them. How each is decided is at toolgpa.com/grades. This guide is ToolGPA’s own work; it is not made, paid for or approved by Mails, Inc. Prices change, so check mails.so before you buy.
Part 07 · About
About ToolGPA
Who made this guide, what else is on the site, and how to cite it
7,721
Tools graded, in 95 categories
ToolGPA grades software the way a school report grades a pupil: five subjects, a letter for each with the reason written beside it, and a GPA that averages them. Prices, plans and platforms are read from each maker’s own pages and dated, so you always know how fresh a figure is.
Every grade, review and ranking on ToolGPA is our own judgement. No company can pay for a grade or change one. Every tool on the site has a guide like this one, free to download and pass on. It all lives at toolgpa.com.
7,721
tools graded
95
categories
739
price changes on record
579
apps priced in 12 countries
What else is on toolgpa.com
- Mails.so, kept up to dateEverything in this guide, with prices and grades as they are todaytoolgpa.com/tools/mails-so
- How grades are givenThe rules behind every letter and every GPAtoolgpa.com/grades
- Value chartsWhat each tool costs against what it scores, for every categorytoolgpa.com/charts
- CompareAny two tools side by side, plan by plantoolgpa.com/compare
- Price changesEvery price rise and cut on record, each with its sourcetoolgpa.com/price-changes
- Prices by countryWhat apps cost on the App Store in 12 countriestoolgpa.com/prices-by-country
- Pay lessEvery public discount: yearly billing, students, nonprofitstoolgpa.com/save
- Keep or makeWhich tools are worth paying for, and which you could build yourselftoolgpa.com/keep-or-make
Scan for the live page
Prices and grades as they are today
Quoting this guide?
Please name ToolGPA and link to the live page, so readers can check the figures for themselves:
ToolGPA, "Mails.so: The Insider's Guide", checked Nov 13, 2026. https://toolgpa.com/tools/mails-so
Know someone choosing between email verification and deliverability tools?
Send them this guide: toolgpa.com/tools/mails-so/guide
ToolGPA elsewhere: youtube.com/@toolgpa
See our other guides
The best-graded email verification and deliverability tools after Mails.so, each with an Insider's Guide of its own.
- Email Verification & Deliverability Insider's GuideEvery one of the 63 email verification and deliverability tools we grade, compared
- QuickEmailVerification Insider's GuideBulk email list cleaning and a real-time verification API3.0 GPA
- Mail-Tester Insider's GuideSend an email to a test address and get a spam score out of 102.8 GPA
- Reoon Email Verifier Insider's GuideBulk and real-time email verification with refunds on unknowns2.8 GPA
Choosing software? Every tool graded, every price dated.
Compare tools at toolgpa.com ›Everything in this guide is ToolGPA’s own summary of what Mails.so’s pages, its app-store listings and public reviews said on the dates shown. Grades are our judgement under the rules at toolgpa.com/grades. Every grade, review and ranking on ToolGPA is our own judgement. No company can pay for a grade or change one. Mails.so is a trademark of its owner, and this guide is not made, paid for or approved by Mails, Inc. Prices and plans change: check mails.so before you buy.