I posted VaultSandbox two months ago and the main feedback was AGPL concerns. I've listened: it's now Apache 2.0. I've also overhauled the local experience to make it "just work" on localhost with zero config.
VaultSandbox is a self-hosted SMTP receiver and programmable debugger. It bridges the gap between "it sent" and "it was delivered" by simulating production-grade email lifecycles. It is architected for parallel testing: each test runs in its own isolated inbox with dedicated webhooks and chaos settings...no state leaks.
What’s New: -Local-First: Encryption (TLS) and email auth (SPF/DKIM) are now optional toggles. On localhost, they are off by default so you can test instantly. -Chaos Mode: Trigger greylisting, latency, or specific SMTP errors per-inbox to test your app's resilience. -Webhooks & Spam Scores: Inbox-scoped webhooks and integrated spam scoring (via rspamd) to predict deliverability before you send. -Instant DNS (vsx.email): Any public IP running VaultSandbox gets a subdomain with pre-configured MX, SPF, DKIM, and DMARC records for high-fidelity testing. -Deterministic Testing: Use our SDKs to "wait" for emails based on specific criteria instead of using sleep() in your tests.
Workflow: 1-Start local: One container gives you SMTP, Web UI, and SDKs. 2-Scale to production: Deploy to a public IP to test real flows from SES/SendGrid with the same test code. No mocks, just reality.
Repo: https://github.com/vaultsandbox/gateway (Apache 2.0) Quick start: https://vaultsandbox.dev/deployment/local-development/
What would it take for you to switch from your current email testing setup?