Mail-Tester
Send an email, get a score out of ten, fix what it tells you
Mail-Tester is a spam-score checker that gives any email a rating out of ten: you send your message to a one-off address it generates, and it reports back on SpamAssassin scoring, SPF, DKIM, DMARC, broken links, HTML problems, blacklist status, and mail server configuration. Three tests a day are free with no account, and paid subscriptions add volume, an API, and white-labelling.
Overview
Mail-Tester is the tool almost everyone in email has used at least once, usually without paying and usually without knowing who runs it. The interaction is the whole product: the page shows you a randomly generated address, you send your campaign or your cold email to it, you click through, and you get a score out of ten with a line-by-line explanation of everything that cost you points. No account, no setup, no connecting a mailbox. That low friction is why it became the default reference point for whether a message is technically clean.
What sits behind the score is SpamAssassin, the open-source filter that a great many mail servers actually run, plus checks on the sending IP, the authentication records, the HTML, the links, and blacklist status. That makes the result concrete in a way a proprietary score is not: when Mail-Tester deducts points, it names the SpamAssassin rule that fired. It also makes the limits clear. A ten out of ten means your message is technically well-formed and your authentication is in order. It does not mean Gmail will put you in the primary tab, because Mail-Tester is not testing placement at named providers the way GlockApps or Unspam do.
The free tier is three tests in any rolling 24 hours, with results kept for seven days, which is genuinely enough for the occasional check that most small senders need. Paid plans exist for people doing this at volume or building it into something: 50 tests a month is $10, 500 is $25, 2,000 is $80, and 7,500 is $250, which works out from 20 cents a test down to about three and a third cents. Creating an account also extends result retention to 30 days and removes advertising from your result pages.
The commercially interesting part is what the paid account unlocks beyond volume. There is a JSON API and an iframe embed, full CSS control over the result page, complete white-labelling once you point your domain at their servers, and a micro-payment mode that lets you charge your own users for tests and take a cut. Several email tools you have used have Mail-Tester underneath. The operators describe themselves only as geeky email software engineers who built it for their own needs, and the service has been running for over a decade, which is a longer track record than most of this category.
Best for
Anyone who needs a fast, credible answer to whether a specific message is technically clean before sending it, and developers who want that answer inside their own product through an API or an embedded, white-labelled result page.
Not the right fit for
- Teams who need inbox placement across named providers; this scores your message against a filter, it does not tell you whether Gmail filed you under Promotions.
- Anyone wanting continuous monitoring; Mail-Tester runs when you ask it to and keeps no watch over your reputation between tests.
- Mailbox warming, which it does not do at all; pair it with a warming tool rather than expecting it to replace one.
- Buyers who need an auditable vendor relationship; the operators publish almost nothing about themselves, and there is no compliance documentation.
- Teams that need quotas to roll over; unused monthly tests expire at the end of the cycle.
How it works
- 1
The page generates a unique test address. You send the email you actually care about to it, from the system that will really be sending it, which is the important detail: the test measures your live sending path rather than a simulation of one.
- 2
You open the result page. A test only counts when all three things happen, the message arrives, you open the result, and the report generates successfully, so a failed send or an unopened result does not consume anything.
- 3
The report scores out of ten and itemises what lost points: SpamAssassin rules that fired, missing or misaligned SPF, DKIM, and DMARC, blacklist listings on the sending IP or domain, broken links, and HTML issues such as a poor text-to-image ratio.
- 4
You fix, resend, and retest. Paid accounts add a JSON API so this loop can run from a script or a build pipeline, an iframe for embedding results in another product, and white-labelling for presenting it as your own.
Feature breakdown
26 features in 5 modulesThe test itself
What the score is actually made of.- Score out of ten
- A single number with five bands from 0 to 3 at the worst to 9 to 10 at the best, which is why it became a shorthand people quote to each other.
- SpamAssassin analysis
- The score is built on SpamAssassin, the open-source filter many real mail servers run, and the report names the specific rules that fired rather than giving an opaque verdict.
- SPF, DKIM, and DMARC checks
- Authentication is validated on the message as actually sent, including alignment, which catches the broken include or the unpublished selector that silently sinks a campaign.
- Blacklist checks
- The sending IP and domain are checked against blacklists as part of the same report, so a listing shows up before the campaign does.
- Broken link detection
- Links in the message are checked, and short URLs are flagged, both of which are common and avoidable point-losers.
- HTML and content analysis
- Text-to-image ratio, malformed markup, and content patterns that trip filters are itemised with the points they cost.
- Mail server configuration review
- The report covers the server and sending IP, not just the message, so misconfiguration upstream of the content is visible.
- Tests your real sending path
- Because you send from the system you will really use, the result reflects your actual infrastructure rather than a relay, which is the same principle that makes account-based placement tests worth more than generic ones.
Free access
The reason everyone has used it.- Three tests every 24 hours, free
- A rolling daily allowance with no account and no card, which covers the occasional check most small senders actually need.
- No signup at all
- The free path requires nothing: open the page, copy the address, send, click. Almost nothing else in this category lets you get a real answer that fast.
- Results kept seven days
- Free results stay available for a week, long enough to share a link with whoever needs to fix the template.
Paid subscriptions
Volume, retention, and a clean result page.- Four published volume tiers
- 50 tests a month for $10, 500 for $25, 2,000 for $80, and 7,500 for $250, with the per-test rate falling from 20 cents to about 3.3 cents.
- One-time payments as well as subscriptions
- Occasional heavy users can buy without committing to a monthly plan, which suits agencies with lumpy testing needs.
- Thirty-day result retention
- An account with a custom prefix extends how long results stay available from seven days to thirty.
- Advertising removed
- Paid accounts show no advertisements on result pages, which matters most when you are sending those links to clients.
- Custom test address prefix
- Account holders get a recognisable prefix rather than a random string, which makes repeated testing less error-prone.
- Usage statistics
- Daily, weekly, and monthly usage reporting plus a listing of every test performed in the last 30 days.
Embedding and resale
The part that explains why Mail-Tester is inside other products.- JSON API
- Results are retrievable programmatically, so the test can run inside a build pipeline, a script, or another product rather than in a browser tab.
- iframe embedding
- The result page can be dropped into your own application without rebuilding the report.
- Custom CSS on results
- The result page is restyled to match your product, which is the difference between an embed that looks borrowed and one that looks native.
- Full white-label
- The service can be presented entirely as your own once their servers are authorised to receive mail for your domain, so your users never see the Mail-Tester brand.
- Micro-payment mode
- You can charge your own users per test and earn a share, which turns the tool into a revenue line for a product rather than a cost. Nothing else in this category offers that.
Free adjacent tools
What else the site gives away.- SPF and DKIM checkers
- Standalone record lookups and validators, free and without an account.
- DMARC utilities
- Record generation and inspection tools alongside the main test.
- BIMI lookup
- Checks whether a brand indicator record is published and valid.
- Domain scanning and phishing link verification
- Ancillary checks that round out a pre-send review without needing a second tool.
Use cases
4 documentedFounder about to launch a first cold campaign
Everything is configured, probably, and there is no way to know whether the message is technically clean before real prospects receive it.
One free test returns a score out of ten with every deduction itemised. Most first-time setups lose points on DKIM alignment or a missing DMARC record, and both are visible in a minute.
Agency proving a fix to a client
A client's campaigns were landing in spam, the team has changed the authentication and the template, and the client wants evidence rather than assurances.
A paid account removes advertising and keeps results for 30 days, so before-and-after result links can be sent to the client as the proof, without a third-party logo on the page.
Developer adding deliverability to a product
The product needs to tell users whether their email setup is sound, and building a spam scorer in-house is out of the question.
The JSON API and iframe deliver the report, custom CSS makes it look native, white-labelling removes the Mail-Tester name, and micro-payment mode can even make the feature pay for itself.
Team running a pre-send checklist
Every campaign is supposed to be checked before launch, but the check keeps being skipped because the tooling is slow.
The 500-test plan at $25 a month is about five cents a test, cheap enough that testing every send stops being a decision and becomes a habit.
Pricing
from $0 (3 tests per 24 hours), then $10 per month for 50 testsFree for three tests every 24 hours with no account. Paid subscriptions are priced by monthly test volume, with one-time payment options alongside, and the per-test rate falls as volume rises. Quotas reset monthly and do not roll over.
| Plan | Price | Includes |
|---|---|---|
| Free | $0 3 tests per 24 hours |
The reason the tool is ubiquitous: a real answer in under a minute with nothing to sign up for. |
| 50 tests a month | $10 per month, excluding VAT ($0.20 per test) |
|
| 500 tests a month | $25 per month, excluding VAT ($0.05 per test) |
|
| 2,000 tests a month | $80 per month, excluding VAT ($0.04 per test) |
Marked most popular, which says something about who the paying customers are: products embedding it, not individuals. |
| 7,500 tests a month | $250 per month, excluding VAT ($0.0333 per test) |
|
Billing notes
- The free allowance is three tests in any rolling 24 hours, not three a month, which is far more generous than it first sounds for a small sender.
- A test counts only when the message arrives, you open the result, and the report generates. Reopening the same result page does not consume another test.
- Monthly quotas reset at the start of each billing cycle and do not roll over, so buy against the volume you actually run rather than a peak month.
- Prices are quoted excluding VAT, which matters for buyers in the EU and UK comparing against VAT-inclusive rivals.
- One-time payments exist alongside subscriptions for lumpy usage, and some long-standing accounts still hold legacy credit balances from the older model.
- Per-test economics improve sharply with volume: 20 cents at the $10 plan against about 3.3 cents at the $250 plan, a sixfold difference.
Value assessment: Judged as a free tool, Mail-Tester is the best value in this category and it is not close: three real tests a day, built on SpamAssassin, with no account, covers the entire pre-send checking need of a small sender at no cost. Judged as a paid product it is narrow but priced honestly, and the buyers who get the most from it are not individuals at all but products embedding the report through the API and white-label. What it does not do should decide the purchase: no placement testing at named providers, no monitoring, no warming. If the question is whether this specific message is technically clean, nothing is faster or cheaper. If the question is where your mail is landing at Gmail this week, you need GlockApps, Unspam, or a warming platform with testing built in.
Strengths & limitations
Strengths
- Three genuinely free tests every 24 hours with no account, which is the lowest-friction real answer available anywhere in this category.
- Built on SpamAssassin, so deductions name a specific rule rather than an opaque proprietary score.
- Tests your actual sending path, because you send from the system you will really use rather than through a relay.
- Covers authentication, blacklists, links, HTML, and server configuration in one report rather than across four tools.
- A JSON API, iframe embedding, custom CSS, and full white-labelling make it genuinely useful as a component inside another product.
- Micro-payment mode lets a product charge its own users for tests and take a share, which nothing else here offers.
- Over a decade of continuous operation, which is a longer track record than most of the category.
- Per-test cost falls to about three cents at volume, cheap enough to test every send rather than the important ones.
Limitations
- It scores a message against a filter; it does not test inbox placement at Gmail, Outlook, and Yahoo the way GlockApps, Unspam, or a seed-list product does.
- No monitoring of any kind. It answers when asked and watches nothing in between, so reputation drift is invisible to it.
- No warming, no sending, and no reputation management, so it is always one tool in a stack rather than the stack.
- The operators publish almost nothing about themselves: no company name, no founders, no location beyond being French, and no compliance documentation.
- Monthly quotas do not roll over, so an unused allowance is simply lost.
- A ten out of ten is routinely over-read as a guarantee of inbox placement, which it is not, and the tool does little to discourage that reading.
- Prices exclude VAT, so the real cost for European buyers is above the advertised number.
Head-to-head comparisons
6 alternativesMail-Tester vs GlockApps
from $59/mo (Essential, billed annually)Different questions. Mail-Tester scores one message against SpamAssassin and tells you what is technically wrong with it, free, in under a minute. GlockApps sends to a seed list and tells you where the message actually landed at Gmail, Outlook, Yahoo, and the rest, with continuous DMARC processing, uptime monitors, and IP reputation monitoring behind a $59 a month Essential plan. Use Mail-Tester before every send because it costs nothing; buy GlockApps when you need to know placement by provider and want the monitoring that surrounds it. Most serious senders end up with both, and the free tier means that costs no more than GlockApps alone.
Full Mail-Tester vs GlockApps comparisonMail-Tester vs MailGenius
from $0 (free spam test), then $23 per month (Beginner)The closest direct comparison: both are spam-score checkers built around sending a message to a generated address. MailGenius charges $23 a month for 60 tests and $39 for unlimited, adds an AI consultant, copywriting analysis, and competitor email testing, and its top tier at $79 tests every email you send automatically. Mail-Tester gives three tests a day free, charges $25 for 500, and adds an API, white-labelling, and resale that MailGenius does not. Take MailGenius for the coaching layer and automatic testing; take Mail-Tester if you want the cheapest credible score or you are embedding it in your own product.
Full Mail-Tester vs MailGenius comparisonMail-Tester vs Unspam
from $0 (Free, 21 tests a month), then pay per test on CustomBoth are cheap pre-send checkers with real free tiers, and they overlap less than they look. Unspam bundles spam testing with inbox placement, rendering previews across 50-plus clients, screenshots, and heatmaps, giving 21 tests a month free and pay-per-test above that. Mail-Tester does one thing, scores a message with SpamAssassin, and does it three times a day for free with a much cleaner API story. Choose Unspam when design rendering and placement matter alongside the score; choose Mail-Tester when the score is the whole requirement or you need to embed it.
Full Mail-Tester vs Unspam comparisonMail-Tester vs MailerCheck
from $10 (1,000 credits, pay as you go)Adjacent rather than competing. MailerCheck is primarily list verification at a cent per address, with inbox placement and email insights costing 200 credits a test. Mail-Tester does not verify lists at all; it checks whether a message and its sending setup are clean. A team doing outbound properly needs both jobs done, and the combination is cheap: free daily scores from Mail-Tester plus $10 of MailerCheck credits covers a small programme's pre-send checks entirely.
Full Mail-Tester vs MailerCheck comparisonMail-Tester vs Folderly
from $96 per mailbox per month billed annually (Folderly), or $0 (Inbox Insights and Pulse free tiers)Opposite ends of the market. Folderly is managed sender reputation at $96 a mailbox a month on annual billing, with continuous monitoring, technical auditing, warm-up, and repair, plus its own Inbox Insights testing product that is free for two tests a month. Mail-Tester is a free score with a $10 entry plan and no monitoring, warming, or account management whatsoever. If deliverability is a standing operational problem worth four figures a month, Folderly. If you need to know whether tomorrow's campaign is clean, Mail-Tester answers that for nothing.
Full Mail-Tester vs Folderly comparisonMail-Tester vs MailStrike
from $18 per mailbox per month billed annually ($23 monthly) for the first five mailboxesComplementary rather than alternatives. MailStrike warms mailboxes with an AI Agent each, writing threads at send time, scores reputation daily, and includes a placement test per mailbox per month sent from your own account, from $18 a mailbox a month. Mail-Tester does no warming and no monitoring; it scores a single message on demand and costs nothing to use three times a day. The sensible pattern is both: Mail-Tester while you are drafting and fixing the template, a warming and monitoring platform standing behind the mailboxes that will send it.
Full Mail-Tester vs MailStrike comparisonPairs well with
8 categoriesMail-Tester is a deliverability tool, and a team running it still has 8 neighbouring categories to staff. The pick in each is Instantly for cold email outreach, InboxKit for cold email infrastructure, ZeroBounce for email verification, Mailchimp for email service providers, Reply.io for sales engagement, AiSDR for AI SDR agents, HubSpot CRM for sales CRM and Google Analytics 4 for GTM analytics, each the leading tool in that category on published criteria.
- InstantlyCold Email Outreach · Category Leader
- Because
- Mail-Tester lists it scores a message against a filter among its limits. Instantly adds bundled validation, tracking domains, and ESP matching bake deliverability hygiene into defaults.
- Benefit
- Outreach goes out on a schedule and replies land in one place instead of a personal inbox.
- InboxKitCold Email Infrastructure · Category Leader
- Because
- Mail-Tester is built for deliverability, not infrastructure. InboxKit adds InfraGuard monitoring covering more than fifty blacklists on a six-hour cycle.
- Benefit
- Sending moves off the main domain, so a burned domain costs a spare rather than the company's email.
- ZeroBounceEmail Verification · Category Leader
- Because
- Mail-Tester is built for deliverability, not verification. ZeroBounce covers verification on its own.
- Benefit
- Dead addresses come off the list before the send, so the bounce rate never touches the domain.
- MailchimpEmail Service Providers · Category Leader
- Because
- Mail-Tester is built for deliverability, not ESPs. Mailchimp adds genuine breadth in one account.
- Benefit
- An opt-in audience is owned rather than rented, and reaching it costs nothing per send.
- Reply.ioSales Engagement · Category Leader
- Because
- Mail-Tester is built for deliverability, not engagement. Reply.io adds Email Volume plan.
- Benefit
- One cadence covers email, calls and LinkedIn, so nobody drops a follow-up between tools.
- AiSDRAI SDR Agents · Category Leader
- Because
- Mail-Tester is built for deliverability, not AI SDR. AiSDR adds metering by researched contacts rather than emails sent.
- Benefit
- Research, writing and sending happen without a headcount, and the meetings still get booked.
- HubSpot CRMSales CRM · Category Leader
- Because
- Mail-Tester is built for deliverability, not CRM. HubSpot CRM adds professional workflow builder.
- Benefit
- Every conversation ends up on a record, so a rep leaving does not take the pipeline with them.
- Google Analytics 4GTM Analytics · Category Leader
- Because
- Mail-Tester is built for deliverability, not analytics. Google Analytics 4 adds free raw event export to BigQuery.
- Benefit
- Spend gets attributed to revenue, so the channel that works is the one that gets funded.
Pairings follow the methodology: the leading tool in each complementary category, chosen on published criteria. Placement cannot be purchased.
Full Mail-Tester stackImplementation & onboarding
- Setup time
- Under a minute for the free test, with nothing to install or connect. An API or white-label integration is a few hours of developer time.
- Learning curve
- Very low to run, moderate to interpret. The report itemises deductions clearly, but knowing which of them genuinely matter, and which are SpamAssassin being pedantic about a template, takes a little experience.
- Onboarding
- Entirely self-serve. Paid plans are bought through Stripe after confirming an email address; white-labelling requires contacting them so their servers accept mail for your domain.
- Migration notes
- Nothing to migrate. It sits alongside whatever you already run and touches no sending infrastructure. Teams replacing an embedded competitor should note the quota model: tests reset monthly and do not roll over, so size the plan against a normal month rather than a launch month.
Platform, API & security
- Platforms
- Web applicationJSON APIiframe embed
- API
- JSON API for retrieving test results programmatically, available on paid accounts, alongside an iframe embed, custom CSS on result pages, and a full white-label mode once the service is authorised to receive mail for your domain.
- Compliance
- None published
- Data residency
- Not published. The service is operated from France.
- SSO
- Not offered; accounts are username and password.
- Security notes
- Test messages are received and parsed by the service, so anything sent to a test address is disclosed to it; use a representative message rather than a live one containing customer data. No SOC 2, ISO certification, or formal security documentation is published.
Support & resources
- Channels
- Contact formEmail
- Documentation
- A FAQ covering how tests are counted, result retention, and the API, plus documentation for the JSON API, iframe, and micro-payment modes.
- Community
- A long-running blog and a wide informal user base; the score out of ten is quoted routinely in deliverability discussions, which is its own kind of validation.
Company
- Founded
- 2014
- Headquarters
- France
- Ownership
- Privately held; the operating company is not named publicly
- Employees
- Not disclosed; described by the operators as a small engineering team
- Funding
- No disclosed funding.
Timeline
- 2014Mail-Tester appears as a free SpamAssassin-backed spam score, built by its authors for their own use and then opened to the public.
- 2018Paid accounts add the JSON API, iframe embedding, and custom CSS, turning the tool into a component other products can build on.
- 2021White-label mode and micro-payment resale let other vendors present the test as their own and earn from it.
- 2026Pricing moves from a credit model to monthly subscriptions at 50, 500, 2,000, and 7,500 tests, with legacy credit balances honoured.
Integrations
- JSON API for any application
- iframe embedding into third-party products
- Works with any sending system, since testing is done by sending a real message
- Stripe for checkout
Frequently asked questions
13 questionsWhat is Mail-Tester?
Mail-Tester is a spam-score checker. It gives you a unique address, you send your email to it from the system that will really be sending, and it returns a score out of ten with an itemised report covering SpamAssassin rules, SPF, DKIM, DMARC, blacklist status, broken links, HTML problems, and mail server configuration.
How many free tests do you get?
Three in any rolling 24 hours, with no account and no credit card. Free results stay available for seven days. That allowance covers the occasional pre-send check most small senders actually need, which is why so many people have used the tool without ever paying for it.
How much does Mail-Tester cost?
Paid subscriptions are $10 a month for 50 tests, $25 for 500, $80 for 2,000, and $250 for 7,500, all excluding VAT, working out from 20 cents a test down to about 3.3 cents. One-time payments are available too. Quotas reset each billing cycle and do not roll over.
Does a 10 out of 10 mean my email will reach the inbox?
No, and this is the most common misreading of the tool. A ten means the message is technically well-formed and your authentication is in order. It says nothing about whether Gmail will file you under Primary, Promotions, or Spam, because Mail-Tester is not testing placement at named providers. For that you need a seed-list product such as GlockApps or Unspam, or a warming platform with placement testing included.
What counts as a test?
All three of these have to happen: your message arrives, you open the result page, and the report generates successfully. Reopening the same result does not count again, and if the message never arrives or you never open the result, nothing is deducted from your allowance.
Can I put Mail-Tester inside my own product?
Yes, and that is who most paying customers are. Paid accounts include a JSON API and an iframe embed, custom CSS so the result page matches your design, and full white-labelling once their servers are authorised to receive mail for your domain. A micro-payment mode also lets you charge your own users per test and take a share.
Is the score based on anything real?
Yes. It is built on SpamAssassin, the open-source filter that a large number of real mail servers run, and the report names the specific rules that fired. That is more transparent than a proprietary score, though it also means the result reflects SpamAssassin's view rather than Google's or Microsoft's.
Who runs Mail-Tester?
That is barely disclosed. The operators describe themselves as geeky email software engineers who built the tool for their own needs, the service is run from France, and it has been going for over a decade. No company name, founders, or compliance documentation is published, which is worth weighing if you plan to embed it in a product you sell.
Does it monitor my reputation over time?
No. Mail-Tester runs when you ask it to and watches nothing in between. Continuous reputation, blacklist, and DNS monitoring is a different job, covered by MailStrike, GlockApps, or a DMARC platform, and Mail-Tester is best used alongside one of those rather than instead of it.
What else is free on the site?
SPF and DKIM checkers, DMARC utilities, a BIMI lookup, domain scanning, and phishing link verification, all usable without an account. For a founder doing a one-off authentication review, those cover most of what a paid DMARC tool would tell you on day one.
What should I pair Mail-Tester with?
Mail-Tester is a deliverability tool, and a team running it still has 8 neighbouring categories to staff. The pick in each is Instantly for cold email outreach, InboxKit for cold email infrastructure, ZeroBounce for email verification, Mailchimp for email service providers, Reply.io for sales engagement, AiSDR for AI SDR agents, HubSpot CRM for sales CRM and Google Analytics 4 for GTM analytics, each the leading tool in that category on published criteria.
What do I pair with Mail-Tester for Cold Email Outreach?
Instantly. Mail-Tester lists it scores a message against a filter among its limits. Instantly adds bundled validation, tracking domains, and ESP matching bake deliverability hygiene into defaults.
Is Mail-Tester enough on its own?
For deliverability, yes. Mail-Tester does not cover cold email infrastructure, email verification and email service providers, and its own profile says so; InboxKit, ZeroBounce and Mailchimp are the tools that fill those gaps.
Editorial verdict
Mail-Tester earns its place in any deliverability stack by being free, fast, and specific. Three tests a day with no account, a score out of ten backed by SpamAssassin, and a report that names the exact rule costing you points is the cheapest useful thing a sender can do before launching a campaign, and the paid tiers are honestly priced for the agencies and products that run it at volume. The API, white-labelling, and micro-payment resale explain why the tool turns up inside other vendors' products, and make it a genuine build-versus-buy answer for anyone adding deliverability checks to their own software. Understand the boundary before relying on it: this is a technical cleanliness check, not a placement test and not a monitor. A ten out of ten tells you nothing about which Gmail tab you landed in, and nothing at all about next week. Use it constantly, for free, alongside a warming and monitoring platform that covers what it deliberately does not.
Written by the SaaSTracker editorial team. Awards, when shown, are judged against the published criteria in our methodology.