Mailtester

MailTester Ninja is an email verification and email finder tool built for teams sending cold outreach and marketing campaigns at volume. It checks whether an address is valid and deliverable across seven checkpoints, and the company reports processing up to a million emails a day across 159 countries at 99% accuracy. Its main differentiator is privacy: the service states that verified addresses are never stored on its servers, which it presents as full GDPR compliance rather than a policy promise. Alongside the verifier, the product includes an email finder for discovering business addresses, a deliverability score test, a REST API, and a downloadable desktop app for working through large lists. The company operates from London, reports more than 100,000 users, and holds a 4-star average across roughly 136 Trustpilot reviews.

Features

• Real-Time Verification: Validates syntax, domain, and mailbox deliverability across seven checkpoints and returns a confidence score with a detailed report.
• Email Finder: Searches for valid business addresses for contacts and companies, so discovery and validation happen in the same subscription.
• Bulk Processing App: A downloadable desktop application runs large lists and matches results back to the original input file.
• Email Checker API: A documented REST API for building verification into signup forms, CRMs, and internal tooling.
• Deliverability Score: A separate test that scores a sending setup, supported by the company's published email infrastructure index.
• No Data Retention: Verified addresses are not stored on the company's servers, which underpins its GDPR positioning.

Pricing

MailTester Ninja publishes flat subscriptions based on daily volume, with no upfront cost and cancellation at any time:

• Free checker: $0. The web verifier checks addresses without a signup, subject to a small per-request limit.
• Starter: $6.99 per week. 50,000 email verifications and 50,000 API calls per day, with 24/7 support.
• Pro: $16.99 per month. 100,000 verifications and 100,000 API calls per day.
• Ultimate: $49.99 per month. 500,000 verifications and 500,000 API calls per day on the company's fastest tier.

Plan quantities can be stacked to multiply daily limits, keys can be issued to several email addresses under one subscription, and payment by Bitcoin is accepted alongside card billing.

Pros

• Very Low Cost Per Verification: Reviewers repeatedly single out the pricing, with daily allowances that undercut per-credit verification vendors substantially.
• Fast and Simple: Trustpilot reviewers describe checking large lists quickly with minimal setup or training.
• Measurable Bounce Reduction: Customers report sharp drops in bounce rate after cleaning lists, including one who cites a fall from 7.5% to 0.2%.
• No Stored Data: Because verified addresses are not retained, teams handling third-party contact data have a simpler compliance story.
• Free Entry Point: The no-signup web checker allows accuracy testing before any subscription is taken out.
• Verification and Discovery Together: Finding addresses and validating them sit under the same plan rather than requiring two vendors.

Cons

• Edge Cases Remain Uncertain: Some reviewers report addresses marked valid that later bounced, and catch-all domains cannot be resolved to a definitive answer.
• Speed Trade-Off: At least one reviewer notes verification can run slower than higher-priced premium tools.
• Daily and API Rate Limits: Volume caps and documented query rates apply per plan, so very high-throughput workflows need throttling or stacked plans.
• Support Response Times: A minority of reviewers mention slower replies than the advertised 24/7 support suggests.
• Narrow Scope: The product verifies and finds addresses but does not handle enrichment, sequencing, or campaign management.
• Review Coverage Concentrated on One Platform: Feedback sits almost entirely on Trustpilot, with little presence on other major software review sites.