Inbucket
Best for self-hosting
Why teams pick it
Teams wanting self-hosted alternatives to cloud-based email testing services
Open-source alternatives to Mailosaur
Compare community-driven replacements for Mailosaur in email testing & sandbox inboxes workflows. We curate active, self-hostable options with transparent licensing so you can evaluate the right fit quickly.
Mailosaur
Mailosaur provides disposable email inboxes and SMS numbers for end-to-end QA. Developers can send, receive, and inspect messages via REST/SMTP with SDKs for Playwright/Cypress, validate content and links, capture attachments, set wait-for rules and webhooks, and run automated tests in CI without contacting real users.Read more
Key stats
- 8Alternatives
- 1Support self-hosting
Run on infrastructure you control
- 6Active development
Recent commits in the last 6 months
- 7Permissive licenses
MIT, Apache, and similar licenses
Counts reflect projects currently indexed as alternatives to Mailosaur.
Start with these picks
These projects match the most common migration paths for teams replacing Mailosaur.
MailDev
Fastest to get started
Why teams pick it
Docker support and Node.js API for flexible deployment
All open-source alternatives
MailDev
Local SMTP server for testing emails during development
Active developmentPermissive licenseFast to deploySCSS
Why teams choose it
- Built-in SMTP server with web UI for viewing captured emails
- Docker support and Node.js API for flexible deployment
- Selective email relay to real SMTP servers for integration testing
Watch for
Requires Node.js runtime or Docker for deployment
Migration highlight
Password Reset Flow Testing
Developers verify reset email content and links without sending to real user addresses during feature development
Inbucket
Disposable email testing server with zero external dependencies
Self-host friendlyActive developmentPermissive licenseGo
Why teams choose it
- Self-contained binary with built-in SMTP, POP3, HTTP servers and storage
- Accepts email for any address without pre-configuration or user management
- RESTful API with official Go client for programmatic message retrieval
Watch for
Not designed for production email delivery or long-term message retention
Migration highlight
Automated Integration Testing
CI/CD pipelines validate email content and delivery logic without external dependencies or API rate limits
MailHog
Lightweight email testing tool with web UI and API
Permissive licenseIntegration-friendlyAI-powered workflowsGo
Why teams choose it
- Zero-installation binary runs on multiple platforms without dependencies
- Real-time web UI with EventSource updates and multipart MIME support
- JSON API (v1/v2) for automated testing and message retrieval
Watch for
In-memory default storage loses messages on restart
Migration highlight
PHP Application Testing
Configure php.ini to route sendmail through MailHog, inspect registration and password reset emails locally without external SMTP
Papercut
Desktop SMTP server and email viewer for development
Active developmentFast to deployIntegration-friendlyC#
Why teams choose it
- Built-in SMTP server (receive-only) with instant desktop email viewer
- Complete email inspection: HTML rendering, headers, MIME sections, attachments, and raw view
- System tray integration with new message notifications
Watch for
Windows-only desktop application (requires WebView2 component)
Migration highlight
Web Application Registration Flow Testing
Developers verify welcome emails, activation links, and HTML rendering without configuring external SMTP servers or risking accidental sends to real addresses.
Mailpit
Fast, zero-dependency email testing tool for developers
Active developmentPermissive licenseFast to deployGo
Why teams choose it
- Single static binary with zero dependencies and multi-platform Docker images
- Modern web UI with real-time updates, advanced search, and HTML/spam/link testing
- REST API for automated integration testing and optional POP3 server
Watch for
Default 500-email retention limit requires configuration adjustment for larger test suites
Migration highlight
Local Development Email Capture
Developers test registration flows, password resets, and notifications without sending real emails or configuring external services
Smtp4dev
Advanced fake SMTP server for realistic email testing
Active developmentPermissive licenseFast to deployC#
Why teams choose it
- Advanced web UI with viewport switcher for responsive testing
- Built‑in IMAP server and TLS/SSL with auto‑generated certificates
- OpenAPI/Swagger documented REST API for message management
Watch for
Requires .NET runtime, may be heavier than lightweight Go tools
Migration highlight
Responsive email design verification
Render emails in various viewport sizes to ensure layout works on mobile and desktop clients
MailCrab
Lightweight Rust‑based email sandbox with web UI and API
Active developmentPermissive licenseFast to deployRust
Why teams choose it
- Accept‑all SMTP server with configurable ports
- Browser‑based UI for viewing, downloading, and inspecting messages
- Single binary distribution; 7.77 MB Docker image for amd64/arm64
Watch for
Messages stored only in memory; no built‑in persistence
Migration highlight
CI Test Suite Integration
Capture and assert email contents during automated builds without external services.
MailCatcher
Capture and view outgoing email locally via a simple web UI
Permissive licenseFast to deployIntegration-friendlyRuby
Why teams choose it
- Intercepts all outgoing mail via a local SMTP server
- Web UI shows HTML, plain‑text and source with inline image rendering
- Real‑time updates via WebSockets or periodic refresh
Watch for
Not intended for production email routing
Migration highlight
Rails development email preview
Developers see rendered email in the browser instantly, speeding up template iteration.
Choosing a email testing & sandbox inboxes alternative
Teams replacing Mailosaur in email testing & sandbox inboxes workflows typically weigh self-hosting needs, integration coverage, and licensing obligations.
- 1 project let you self-host and keep customer data on infrastructure you control.
- 6 options are actively maintained with recent commits.
Tip: shortlist one hosted and one self-hosted option so stakeholders can compare trade-offs before migrating away from Mailosaur.