Email Testing Tool for Developers

MailLinter uses Apache SpamAssassin to analyze your emails and provide a detailed spam score breakdown. Send your email to MailLinter's SMTP server, and it will show you exactly which spam rules were triggered, what score each rule added, and specific recommendations to improve deliverability. Scores below 5.0 are generally considered safe for inbox delivery.

MailLinter tests compatibility across 15+ email clients covering 95.7% of market share, including Gmail (web and mobile), Outlook (2019, 2021, web, and mobile), Apple Mail (macOS and iOS), Yahoo Mail, Samsung Mail, Thunderbird, and more. It identifies CSS properties, HTML elements, and features that may not render correctly in specific clients.

MailLinter integrates with OpenAI GPT-4o and Anthropic Claude to provide intelligent deliverability analysis. The AI ingests all test results—spam scores, accessibility issues, compatibility problems—and synthesizes them into prioritized, actionable recommendations. It generates a Deliverability Score and provides specific fixes ranked by impact, helping you focus on changes that will most improve inbox placement.

Yes, MailLinter is completely free to use and all features are currently available at no cost, including AI analysis with GPT-4o and Claude (you provide your own API key). We plan to introduce an annual license that will unlock premium features like team sharing, login protection for restricted access, and AI capabilities layer. These features are currently in beta as we consider that it's the best way to collect feedback from our users. Core email testing—spam scoring, accessibility checking, and compatibility testing—will always remain free.

MailLinter automatically checks your HTML emails against WCAG 2.0 accessibility guidelines. It scans for missing alt text on images, improper heading hierarchy, insufficient color contrast, missing language attributes, and other accessibility issues. Each issue is categorized by severity (critical, serious, moderate, minor) with specific recommendations for fixes.

Yes, MailLinter provides a REST API that you can integrate into your CI/CD pipeline. You can programmatically send emails, retrieve analysis results, and set up automated checks for spam scores, accessibility issues, and compatibility problems. This allows you to catch email issues before they reach production.

MailLinter uniquely combines AI-powered deliverability analysis with comprehensive email testing. The AI doesn't just check individual issues—it synthesizes all test results (spam, accessibility, compatibility) into a unified Deliverability Score with prioritized, actionable fixes. Unlike cloud services, it runs locally via Docker, keeping your email content private. No account required, instant results, and the AI layer provides insights that traditional tools simply can't match.