# MailboxValidator

> MailboxValidator is an email validation service running from Penang, Malaysia since 2013 that connects to the receiving mail server in real time without sending a message, and sells two entirely separate products: prepaid bulk plans from $19.95 for 1,000 queries to $699.95 for a million, and monthly API subscriptions from a permanently free 300 queries a month up to $339.95 for 375,000. It publishes SDKs for eleven languages, roughly twenty platform integrations including an MCP connector, and a genuinely unusual set of caveats: bulk credits expire after 30 days, Yahoo addresses cannot be validated at all, non-ASCII addresses are marked invalid, and there are no refunds.

- Category: Email Verification (https://saastracker.org/categories/email-verification)
- Website: https://www.mailboxvalidator.com
- Starting price: $0 for 300 API queries a month or a 100-query bulk trial, then $19.95 for 1,000 bulk queries
- Free plan: API-FREE gives 300 queries a month indefinitely with standard support. An invitation-only API-FREE+ plan doubles that to 600.
- Free trial: A free bulk trial plan with 100 queries, plus a permanently free API plan with 300 queries per month
- Founded: 2013, HQ: Bayan Baru, Penang, Malaysia, Ownership: Privately held and independently operated
- Profile last reviewed: 2026-08-22
- Canonical profile: https://saastracker.org/products/mailboxvalidator

## Overview

MailboxValidator has been running continuously since 2013 from Penang, Malaysia, which makes it one of the longest-lived independent verifiers in the category and one of the smallest, with public directories putting it at a handful of staff. It has validated more than 1.3 billion addresses and found about 206 million of them bad, and it claims a 96 percent deliverability figure, which is notably more modest than the 99 percent everyone else advertises and reads as more honest for exactly that reason.

The product is unmistakably developer-first. There are SDKs for Node.js, Ruby, PHP, Perl, Python, Java, .NET, Go, Rust, Kotlin, and Scala, which is more language coverage than any other vendor profiled here, alongside platform extensions and roughly twenty integrations spanning Zapier, Make, Mailchimp, HubSpot, SendGrid, Mailgun, Campaign Monitor, Mailjet, Intercom, and an MCP connector. The free API plan gives 300 queries a month forever, not as a trial, which makes it a plausible default for a small application that only needs occasional verification.

The pricing is refreshingly literal. Two flat tables, one for bulk and one for API, with a stated processing-time expectation attached to each bulk tier, from under an hour for 100 queries to under 72 hours for a million. There is no calculator, no coupon, no dynamic currency rendering, and no sales gate. At $199.95 for 100,000 addresses and $699.95 for a million, the bulk table is one of the cheapest published anywhere, cheaper per address at the top than EmailListVerify or ListWise and approaching MyEmailVerifier territory.

What you have to weigh against that is an unusually specific list of things the service will not do. Bulk credits expire 30 days after purchase, which is the shortest expiry of any vendor here by a wide margin. Yahoo addresses cannot be validated at all, which is a real functional hole on any consumer list. Non-ASCII addresses are marked as invalid syntax rather than handled. And the FAQ states plainly that no refunds are offered. Every one of those is disclosed openly rather than buried, which is to the vendor's credit, but together they define who this product is and is not for.

## How it works

1. For bulk work you upload a mailing list as a text or CSV file to the portal and wait. Each bulk tier carries a published processing-time expectation, from under four hours at 1,000 to 10,000 queries up to under 72 hours at a million, which is slower than most competitors and stated honestly rather than glossed over.

2. Each address is checked by connecting to the mail server in real time. MailboxValidator states explicitly that it never sends an email to the recipient during checking, only testing the SMTP connection, so nothing arrives in a prospect's inbox as a result of verification.

3. Alongside the connection test, the service runs syntax validation, MX record checks, an MX server connection test, greylisting detection, free provider identification, disposable provider detection, role account detection, a check against MailboxValidator's own suppression list, DMARC enforcement and strict SPF checks, a website existence check, and duplicate removal.

4. For real-time use, the REST API returns JSON or XML per address and is available on a permanently free 300-query monthly plan or on paid monthly subscriptions with auto-renewal and auto-recharge. Eleven language SDKs and roughly twenty platform integrations mean most implementations are configuration rather than engineering. Validation results remain accessible in your account for up to a year.

## Best for

Developers and small technical teams who want a cheap, long-lived, no-nonsense validation API with SDKs in their own language, a free tier that never ends, and a flat published price table, and whose lists are B2B or non-Yahoo enough that the provider gap does not matter.

## Not the right fit for

- Anyone with a meaningful share of Yahoo addresses on their list, because MailboxValidator states outright that its system does not support validating them, which on a consumer list is a serious hole.
- Buyers who need internationalised addresses handled, since any address containing a non-ASCII character is marked as invalid syntax rather than validated.
- Teams buying credits ahead of a project, because bulk credits expire 30 days after purchase and there are no refunds, which is the harshest combination of terms in this category.
- B2B outbound teams needing catch-all resolution, which MailboxValidator does not attempt.
- Anyone who needs results quickly on a large file, since a million-address bulk job carries a published expectation of up to 72 hours.

## Features

### Validation checks

A wide, specifically named battery including several nobody else lists.

- **Email syntax checker**: Validates that the address conforms to standard format, with the caveat that any non-ASCII character causes an invalid-syntax result rather than an internationalised validation.
- **MX record and server connection checks**: Confirms both that mail server records exist in DNS and that a network connection to that server actually succeeds, which are two different failures that many verifiers collapse into one.
- **Real-time SMTP connection without sending**: The service connects to the SMTP server in real time to test the mailbox and explicitly does not send a message to the recipient, so verification is invisible to the person being checked.
- **Greylisting checker**: Identifies servers using greylisting or honeypot-style deferral behaviour, surfacing it as a distinct condition rather than as a generic unknown.
- **Suppressed email checker**: Checks each address against MailboxValidator's own accumulated Do Not Mail list, which is a form of shared reputation intelligence that individual verifiers rarely expose.
- **Role account detection**: Flags addresses such as admin@, webmaster@, and tech@, which the vendor notes are commonly rejected by sending providers because they may be lists with recipients who never opted in.
- **Disposable provider detection**: Identifies throwaway providers such as Mailinator, with a standalone free disposable email validation tool published separately.
- **Free email provider detection**: Marks addresses at consumer providers such as Gmail, useful for B2B scoring and signup quality checks.
- **DMARC enforced and strict SPF checkers**: Verifies the sending domain's authentication posture, which is authentication intelligence about the domain rather than deliverability of the mailbox, and is unusual to find inside a verifier.
- **Website exists checker**: Checks whether the domain actually hosts a website, a rough but useful signal about whether a business domain is real and active.
- **Duplicate email remover**: Strips repeated addresses in a list so credits are not spent twice on the same contact.

### Developer surface

The widest SDK coverage of any verifier profiled here.

- **SDKs in eleven languages**: Node.js, Ruby, PHP, Perl, Python, Java, .NET, Go, Rust, Kotlin, and Scala modules, which covers ecosystems most competitors ignore entirely.
- **REST API with JSON or XML**: Single validation returns results in either format with sample code published, so integration is a short job in almost any stack.
- **Free API plan forever**: 300 queries a month at no cost with no expiry, which is a genuine permanent free tier rather than a trial, plus an invitation-only 600-query free plan.
- **Separate domain, disposable, and role validation APIs**: Distinct endpoints for validating a whole domain, checking for disposable providers, and identifying role addresses, so you can call only the check you need.
- **Platform extensions**: Published extensions alongside the SDKs for common content and form platforms, so non-developers can add validation without writing code.
- **Response timing transparency**: The API returns a time-taken field, and the vendor explains openly that busy mail servers make some validations slow because the check is genuinely real time rather than cached.

### Integrations

Around twenty named platforms for a company of a handful of people.

- **ESP connectors**: Mailchimp, AWeber, Mailgun, SendGrid, Campaign Monitor, SparkPost, MailerLite, Constant Contact, VerticalResponse, MooSend, Mailjet, and iContact.
- **CRM and messaging**: HubSpot, ActiveCampaign, Intercom, and Autopilot, extending validation past marketing lists into customer records.
- **Automation platforms**: Zapier and Make cover everything without a native connector, which is how a small vendor keeps a long tail supported.
- **ChatGPT and MCP**: A ChatGPT integration and a Model Context Protocol connector let AI assistants call validation directly, which is an early move for a vendor this size.
- **Five-minute setup claim**: The vendor positions integrations as connect-and-go rather than as engineering projects, consistent with the SDK-heavy approach.

### Commercial terms

Two flat tables, cheap rates, and terms you must read before buying.

- **Flat published bulk table**: From $19.95 for 1,000 queries through $59.95 for 10,000, $199.95 for 100,000, and $699.95 for a million, with no calculator and no negotiation.
- **Published processing times per tier**: Under one hour for the free 100-query trial, under four hours up to 10,000, under twelve hours at 50,000, under 24 at 100,000, under 48 at 500,000, and under 72 at a million.
- **Monthly API subscriptions**: Free at 300 queries a month, $29.95 for 3,000, $69.95 for 15,000, $139.95 for 75,000, and $339.95 for 375,000, with auto-renewal and auto-recharge.
- **Free bulk trial with 100 credits**: A no-cost bulk plan with 100 queries and standard support, processed in under an hour, which is enough to test the file workflow end to end.
- **Thirty-day credit expiry**: Bulk credits are valid only for 30 days from purchase. Topping up before expiry sums the balance and resets the clock to 30 days from the newest purchase, which softens but does not remove the constraint.
- **No refunds**: The FAQ states plainly that refunds are not offered, which combined with the 30-day expiry means an unused bulk purchase is simply lost money.
- **One-year result retention**: Validation results remain accessible in your account for up to a year after the job, which is a convenience feature and also a data-handling fact worth noting.

### Data handling and disclosure

Small vendor, plainly stated limits, no certifications.

- **No message ever sent**: The vendor states directly that it does not send email to the recipient during checking and only tests the SMTP connection, which is the GDPR-friendly posture.
- **Lists are never shared**: The FAQ answers the question of whether uploaded lists are shared with an unqualified no.
- **Published physical address**: A real street address in Bayan Baru, Penang, and thirteen years of continuous trading, which is more accountability than several anonymous competitors provide.
- **Openly published limitations**: Yahoo non-support, ASCII-only validation, credit expiry, and the no-refund policy are all stated in public documentation rather than discovered after purchase, which is unusually honest.

## Use cases

- **Developer adding validation to a low-traffic application**: A side project or internal tool needs to reject fake addresses at signup, and paying a monthly subscription for a few hundred checks makes no sense. Outcome: The free API plan covers 300 queries a month forever, the SDK in the project's own language drops straight in, and the paid ladder is there if the application grows.
- **Team working in an unusual language ecosystem**: The backend is written in Rust, Kotlin, or Scala, and every verifier's SDK list stops at Python, PHP, and Node. Outcome: MailboxValidator publishes maintained modules for all eleven of those ecosystems, which turns an integration project into a dependency addition.
- **B2B list owner doing a one-off million-address clean**: A large business list needs cleaning once, the budget is tight, and there is no rush on turnaround. Outcome: The bulk plan costs $699.95 for a million addresses with a published expectation of under 72 hours, which is among the cheapest published million-address prices in the category, provided the work is done inside the 30-day credit window.
- **Operations team auditing domain authentication alongside list quality**: The team wants to know not just whether addresses are valid but whether the domains they are dealing with enforce DMARC and publish strict SPF. Outcome: The DMARC enforced checker and strict SPF checker run as part of validation, and the website existence check adds a rough signal of whether a business domain is genuinely active.

## Pricing

Two entirely separate products with separate ladders: prepaid bulk plans valid for 30 days with published processing times, and monthly API subscriptions with auto-renewal and auto-recharge including a permanently free tier. No refunds on either.

- **Bulk trial**: $0 100 queries, one time. Full bulk workflow; Processed in under one hour; Standard support; No credit card required.
- **Bulk plans**: $19.95 to $699.95 prepaid, valid 30 days. 1,000 queries for $19.95, so $0.02 each; 10,000 for $59.95, so $0.006 each; 100,000 for $199.95, so $0.002 each; 500,000 for $399.95, so $0.0008 each; 1,000,000 for $699.95, so $0.0007 each. Steep volume discounting, but every credit expires 30 days after purchase and there are no refunds.
- **Free API**: $0 per month, 300 queries. 300 real-time validations every month, permanently; Standard support; Full SDK and integration access; An invitation-only tier doubles this to 600. A genuine forever-free API tier, which almost no competitor offers.
- **Paid API plans**: $29.95 to $339.95 per month, by monthly query volume. 3,000 queries for $29.95, so $0.01 each; 15,000 for $69.95, so $0.0047 each; 75,000 for $139.95, so $0.0019 each; 375,000 for $339.95, so $0.0009 each; Auto-renewal and auto-recharge. The API ladder stops at 375,000 a month; higher real-time volumes need a conversation.

Billing notes:

- At the three reference volumes on the bulk table, MailboxValidator costs $59.95 at 10,000 addresses, $199.95 at 100,000, and $699.95 at 1,000,000, or $0.006, $0.002, and $0.0007 per address.
- That makes it expensive at small volume and very cheap at large volume. At 10,000 addresses it costs more than EmailListVerify, ListWise, and MyEmailVerifier; at a million it undercuts EmailListVerify and ListWise substantially and approaches MyEmailVerifier.
- The API ladder is priced separately and higher per query, from $0.01 at 3,000 a month down to $0.0009 at 375,000, which is the normal premium for real-time single calls rather than batch work.
- Bulk credits expire 30 days after purchase. Adding credits before expiry sums the balance and resets the expiry to 30 days from the latest purchase, so a continuous buyer never loses credits and an occasional buyer easily does.
- There are no refunds, stated plainly in the FAQ, which combined with the 30-day expiry makes over-buying a genuine and irreversible loss.
- The vendor does not publish whether unknown results consume a credit, so assume you pay for the attempt.
- Processing time is published per bulk tier, from under four hours at 10,000 to under 72 hours at a million, which is a rare and useful piece of honesty and also a warning that this is not a fast service at volume.

Value assessment: MailboxValidator is excellent value for a developer and questionable value for a marketer. The forever-free 300-query API plan, eleven language SDKs, roughly twenty integrations, and a $0.0007 per-address bulk rate at a million are all genuinely strong for a company of a handful of people trading since 2013. But the terms attached to that price are the harshest in the category: credits expire in 30 days, refunds do not exist, and the service cannot validate Yahoo addresses at all or handle non-ASCII ones. On a B2B list processed promptly, none of those matter and the price is superb. On a consumer list bought ahead of a project that slips, you can lose the whole purchase and still have an unvalidated Yahoo segment. Price this as a cheap, capable tool with sharp edges, and only buy credits you are certain you will spend this month.

## Strengths

- The widest SDK coverage of any verifier here, with maintained modules for Node.js, Ruby, PHP, Perl, Python, Java, .NET, Go, Rust, Kotlin, and Scala.
- A permanently free API plan of 300 queries a month, which is not a trial and makes the service a viable default for a small application.
- One of the cheapest published high-volume rates anywhere, at $199.95 for 100,000 and $699.95 for a million addresses.
- Around twenty named integrations including Zapier, Make, Mailchimp, HubSpot, SendGrid, Mailjet, Intercom, ChatGPT, and an MCP connector, which is a lot of surface for a very small company.
- Published processing-time expectations per bulk tier, which almost no competitor commits to in public.
- A distinctive check set including a suppression list, DMARC enforcement and strict SPF checks, a website existence check, and greylisting detection.
- Thirteen years of continuous operation from a published street address in Penang, with an explicit statement that uploaded lists are never shared and that no message is ever sent to the recipient.
- Unusual honesty about limitations: the Yahoo gap, ASCII-only validation, credit expiry, and the no-refund policy are all published rather than discovered.

## Limitations

- Yahoo addresses cannot be validated at all, which is a serious functional gap on any consumer list and something no competitor profiled here shares.
- Non-ASCII addresses are marked as invalid syntax rather than validated, so internationalised addresses are effectively unsupported.
- Bulk credits expire 30 days after purchase, by far the shortest expiry in the category, and there are no refunds under any circumstances.
- Processing is slow at volume by published admission, up to 72 hours for a million addresses.
- No catch-all resolution, and no published policy on whether unknown results consume a credit.
- No SOC 2, ISO 27001, trust centre, or data residency commitment, and validation results are retained for up to a year in your account.
- The API ladder stops at 375,000 queries a month, so high-volume real-time use requires a conversation the site does not otherwise need.
- A team of a handful of people supporting eleven SDKs and twenty integrations is a real key-person risk, however long the company has been running.

## Comparisons

- **MailboxValidator vs Verifalia**: The two long-lived developer-first verifiers, and Verifalia is the stronger product. It has configurable quality levels, more than forty status codes, retention settable to five minutes, non-expiring credit packs, and it actively chases provider changes at Yahoo rather than declining the domain. MailboxValidator answers with more SDK languages, a forever-free API tier, published processing times, and a cheaper million-address bulk price. Take Verifalia for depth and safety, MailboxValidator for cheap volume and language coverage.
- **MailboxValidator vs MyEmailVerifier**: MyEmailVerifier beats MailboxValidator on almost every commercial axis: about $99 against $199.95 at 100,000, about $349 against $699.95 at a million, 100 free credits every day rather than 300 a month, credits that never expire, full Yahoo support, and a Deep Catch-All Check. MailboxValidator's counters are eleven SDKs, twenty integrations, published processing times, and thirteen years of trading. Unless the SDK coverage decides it, MyEmailVerifier is the better buy.
- **MailboxValidator vs EmailListVerify**: EmailListVerify is cheaper at 10,000 addresses, $27 against $59.95, while MailboxValidator is cheaper at a million. EmailListVerify has non-expiring credits, full provider coverage, and a large free deliverability toolkit; MailboxValidator has far better SDK coverage, more integrations, and a forever-free API plan. The Yahoo gap and 30-day expiry make EmailListVerify the safer general-purpose choice and MailboxValidator the better technical one.
- **MailboxValidator vs DeBounce**: DeBounce is the closer competitor on consumer lists, with full provider coverage, a published bounce-rate guarantee, and clearer terms on unknown results. MailboxValidator undercuts it on high-volume bulk pricing and beats it decisively on developer tooling. If your list contains Yahoo addresses, DeBounce wins by default; if it does not and you want an API with SDKs in your language, MailboxValidator is worth the tradeoff.
- **MailboxValidator vs ZeroBounce**: ZeroBounce is the full-suite premium option with SOC 2 Type 2, ISO 27001, HIPAA, its own data centres, EU or US API routing, and warmup and inbox placement tooling, at several times the price. MailboxValidator has none of that and costs a fraction as much. This comparison is really about whether you are buying an audited vendor or a cheap capable tool, and the answer usually depends on whether anyone reviews your suppliers.

## Implementation

- Setup time: Minutes for both paths. The free bulk trial needs only an upload, and the free API plan plus a language SDK gets a working integration inside an afternoon. Roughly twenty integrations are positioned as five-minute connections.
- Learning curve: Very low technically. The important learning is commercial: understand the 30-day credit expiry, the no-refund policy, and the Yahoo and ASCII limitations before purchase, because all four are the kind of constraint that only hurts after you have paid.
- Onboarding: Entirely self-serve on every published tier. There is no sales gate anywhere below the top of the API ladder, and support is provided by email.
- Migration: Nothing to migrate. The critical pre-purchase test is a provider census on your own list: count what share of addresses are at Yahoo and its regional domains, and count how many contain non-ASCII characters. If either number is material, MailboxValidator will return invalid or unusable results for that segment and no price makes that acceptable. If both are near zero, run the free 100-address bulk trial and the free API plan against a known control set, then buy only the credits you will actually spend within 30 days.

## Platform, API & security

- Platforms: Web portal for bulk uploads, REST API returning JSON or XML, SDKs for Node.js, Ruby, PHP, Perl, Python, Java, .NET, Go, Rust, Kotlin, and Scala, Platform extensions, Zapier and Make
- API: REST API for single validation with JSON or XML responses, plus separate endpoints for domain validation, disposable email validation, and role email validation. Verification connects to the SMTP server in real time, so response time varies with the target server's load and the API returns a time-taken field. Monthly API plans run from a permanently free 300 queries up to 375,000, with auto-renewal and auto-recharge; no per-second rate limits are published.
- Compliance: No certifications published, No message sent to recipients during validation, Uploaded lists stated never to be shared
- Data residency: Not published. The company operates from Penang, Malaysia.
- SSO: Not advertised.
- Security notes: The vendor states plainly that no email is sent to the recipient during checking, only an SMTP connection test, and that uploaded lists are never shared. Validation results remain accessible in the account for up to one year, which is convenient and also means results persist far longer than at vendors offering configurable short retention. There is no published certification, trust centre, penetration test summary, or data residency option.

## Support

- Channels: Email support on paid plans, Standard support on free and trial plans, Contact form
- Documentation: Developer API documentation with sample code, SDK documentation for eleven languages, an integration library, and a detailed FAQ that answers the commercially awkward questions directly.
- Community: No user forum. There is an affiliate programme, a media kit, a newsletter, and a Trustpilot presence.

## Company

- Founded: 2013
- Headquarters: Bayan Baru, Penang, Malaysia
- Ownership: Privately held and independently operated
- Employees: Very small; public directories put the company in the 1 to 5 range
- Funding: No funding disclosed.

Timeline:

- 2013: MailboxValidator launches from Penang, Malaysia as a developer-focused email validation service with a real-time SMTP connection model and no probe sends.
- 2016: Expands SDK coverage well beyond the usual languages, eventually publishing maintained modules for eleven ecosystems including Rust, Kotlin, and Scala.
- 2019: Builds out the integration library across roughly twenty ESP, CRM, and automation platforms, positioned as five-minute connections rather than engineering projects.
- 2023: Adds DMARC enforcement, strict SPF, and website existence checks to the validation battery, extending the product past mailbox existence into domain posture.
- 2026: Publishes ChatGPT and MCP integrations, and reports more than 1.3 billion addresses validated with about 206 million found bad, at a stated 96 percent deliverability.

## Integrations

Zapier, Make, Mailchimp, AWeber, Mailgun, SendGrid, Campaign Monitor, SparkPost, HubSpot, MailerLite, Constant Contact, VerticalResponse, MooSend, Mailjet, iContact, ActiveCampaign, Intercom, Autopilot, ChatGPT, MCP connector

## FAQ

### What is MailboxValidator?

MailboxValidator is an email validation service operating from Penang, Malaysia since 2013. It connects to the receiving mail server in real time to test whether a mailbox exists, without ever sending a message, and runs syntax, MX, greylisting, disposable, role, free-provider, suppression-list, DMARC, SPF, and website-existence checks alongside it. It sells prepaid bulk plans and monthly API subscriptions, including a permanently free 300-query API tier.

### How much does MailboxValidator cost?

Bulk plans are $19.95 for 1,000 queries, $39.95 for 5,000, $59.95 for 10,000, $149.95 for 50,000, $199.95 for 100,000, $399.95 for 500,000, and $699.95 for a million, which works out to $0.006, $0.002, and $0.0007 per address at 10,000, 100,000, and one million. API subscriptions are free for 300 queries a month, then $29.95 for 3,000, $69.95 for 15,000, $139.95 for 75,000, and $339.95 for 375,000.

### Can MailboxValidator validate Yahoo addresses?

No. The vendor states directly in its FAQ that its system does not support Yahoo email addresses. Hotmail addresses are supported. This is the single most important thing to know before buying, because on most consumer lists Yahoo is a meaningful share of the addresses, and no competitor profiled here has this limitation. Count your Yahoo addresses before you spend anything.

### Do MailboxValidator credits expire?

Yes, and quickly. Bulk credits are valid for only 30 days from the date of purchase, which is the shortest expiry of any verifier profiled here. Adding more credits before expiry sums the balance and resets the expiry to 30 days from the newest purchase, so a continuous buyer never loses anything and an occasional buyer easily does. Combined with the stated no-refund policy, an unused bulk purchase is simply lost.

### How does MailboxValidator handle catch-all addresses?

It does not resolve them. The service tests the SMTP connection and reports what the server says, and a catch-all server says yes to everything. There is no equivalent of Truelist's enhanced pass, Scrubby's deep verification, or MyEmailVerifier's Deep Catch-All Check. If a large share of your list sits on accept-all domains, this is not the right tool for that segment.

### Does MailboxValidator send emails to verify addresses?

No, and the FAQ answers this explicitly: the service does not send email to the recipient during checking, it only tests the connection using the SMTP server. That is the same posture as most of the category and the opposite of Scrubby's Deep Verification, which establishes deliverability by actually sending and watching for delayed bounces.

### How long does bulk validation take?

The vendor publishes an expectation per tier, which is unusually transparent: under one hour for the 100-query trial, under four hours for 1,000 to 10,000, under twelve hours at 50,000, under 24 hours at 100,000, under 48 at 500,000, and under 72 at a million. That is slower than most competitors, who typically promise minutes, so plan a large clean into a schedule rather than running it the day before a send.

### What SDKs and integrations does MailboxValidator support?

SDKs for eleven languages: Node.js, Ruby, PHP, Perl, Python, Java, .NET, Go, Rust, Kotlin, and Scala, which is the widest coverage of any verifier here. Integrations span roughly twenty platforms including Zapier, Make, Mailchimp, AWeber, Mailgun, SendGrid, Campaign Monitor, SparkPost, HubSpot, MailerLite, Constant Contact, VerticalResponse, MooSend, Mailjet, iContact, ActiveCampaign, Intercom, Autopilot, ChatGPT, and an MCP connector.

### Is my data safe with MailboxValidator and how long is it kept?

The vendor states that uploaded lists are never shared and that no message is sent to the addresses being checked. Validation results remain accessible in your account for up to one year after the job, which is longer retention than privacy-forward competitors such as Verifalia, where retention is configurable down to five minutes. There is no published SOC 2 report, ISO certification, trust centre, or data residency commitment.

### Who should not use MailboxValidator?

Anyone with a significant Yahoo segment or internationalised addresses, both of which the service cannot validate. Anyone buying credits ahead of a project that might slip, because of the 30-day expiry and no-refund policy. B2B teams who need catch-all resolution. And anyone who needs a large list cleaned quickly, given published processing times of up to 72 hours at a million addresses.

## Editorial verdict

MailboxValidator is a small, honest, long-lived tool that is very good at a specific job and openly bad at several others. Eleven language SDKs, roughly twenty integrations, a permanently free 300-query API plan, and a $0.0007 per-address bulk rate at a million make it one of the best developer-facing options in the category, and the published processing times and openly documented limitations are more candour than most vendors manage. But the limitations are real and unusual: no Yahoo validation at all, no non-ASCII support, credits that expire in 30 days, no refunds, and no catch-all resolution. Those are not deal-breakers for a B2B list processed promptly by a technical team, and they are close to disqualifying for a consumer newsletter or an occasional buyer. Run the provider census on your own list first. If Yahoo is a rounding error and you will spend the credits this month, this is a bargain with excellent tooling. If not, MyEmailVerifier or EmailListVerify does the same work with none of the sharp edges.

---

Source: SaaSTracker (https://saastracker.org), an independent editorial project. This profile is compiled from public information, carries no peer reviews or paid placement, and was last reviewed 2026-08-22. Awards are judged on published criteria: https://saastracker.org/methodology