Mailinator
Disposable email testing inboxes with public and private domains
Open-Source Projects
Discover top open-source software, updated regularly with real-world adoption signals.
Discover top open-source software, updated regularly with real-world adoption signals.
Lightweight Rust‑based email sandbox with web UI and API
MailCrab provides an accept‑all SMTP server and a browser‑based interface to capture, view, and download test emails, all packaged as a single 7.77 MB Docker image.
MailCrab is a Rust‑written email test server designed for developers who need a quick, reliable way to capture outgoing mail during development or CI runs. It runs as a single binary and is distributed as a 7.77 MB Docker image that works on both amd64 and arm64 platforms.
The server accepts all SMTP traffic on a configurable port, stores messages in memory, and exposes a modern web UI where you can inspect formatted content, download attachments, view raw headers, or delete messages. Real‑time updates are pushed via WebSocket, and a simple REST API lets external tools query or manage messages. Configuration options include TLS generation, custom certificates, host/port overrides, path prefixes, retention periods, and queue sizing. Deploy with a one‑liner Docker command, a pre‑built binary, or via Helm for Kubernetes.
MailCrab shines in local development, automated test pipelines, and lightweight staging environments where persistent storage isn’t required, offering fast feedback without the overhead of a full mail server.
When teams consider MailCrab, these hosted platforms usually appear on the same shortlist.
Looking for a hosted option? These are the services engineering teams benchmark against before choosing open source.
CI Test Suite Integration
Capture and assert email contents during automated builds without external services.
Frontend Email Template Debugging
Inspect rendered HTML emails and attachments directly in the browser UI.
Kubernetes Development Environment
Deploy via Helm chart to provide a shared email sandbox for the whole team.
TLS‑Enabled Integration Testing
Validate TLS handshake and basic authentication handling using generated or custom certificates.
Set `ENABLE_TLS_AUTH=true` in the container environment; MailCrab will generate a self‑signed certificate or use mounted key/cert files.
Emails are kept in memory while the process runs; they are cleared on restart unless a retention period is configured.
MailCrab does not include built‑in persistence; you would need to forward messages to external storage via the API or custom tooling.
The WebSocket connection can become a bottleneck above ~100 messages per second; increasing `QUEUE_CAPACITY` helps mitigate loss.
Project at a glance
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