VaultSandbox
Test your real MailGun/SES/etc. integration
Details
- External ID
- 46512203
- Source
- HN
- Company
- —
- Product
- VaultSandbox
- Website domain
- vaultsandbox.com
- Launched
- Jan. 6, 2026
- Cohort
- —
- Upvotes
- 58
- Upvotes percentile
- 0.8293807641633728
- Tags
- —
- Fetched at
- Sept. 7, 2026, 9:25 p.m.
- Updated at
- Sept. 7, 2026, 9:25 p.m.
Description
I've spent the last few months working on something I wish I'd had years ago. I kept running into the same issue: CI green, production mail broken. TLS handshake failures, DKIM alignment mismatches, SPF soft-fails ... the stuff that only surfaces when real mail servers are involved. Most test tools (Mailpit, MailHog) are catch-alls. They confirm "an email was sent" but don't validate the protocol. They also aren't designed for network-exposed environments: no auth, unprotected Web UI, easy to enumerate messages.VaultSandbox is my attempt at fixing that. It's a self-hosted SMTP gateway (AGPLv3) that validates SPF, DKIM, DMARC, and rDNS on every incoming message. You keep your production email provider (Postmark, SendGrid, SES) in tests and you just change the recipient domain. No mocking, no config changes. There are client SDKs (Node, Python, Go, Java, .NET), plus a Web UI and a CLI for manual testing.Some technical details:Deterministic Tests Instead of polling or sleep loops, the SDKs use Server-Sent Events (SSE) so test assertions trigger the moment the mail hits the gateway.Minimal infrastructure footprint Built with NestJS and Angular, with no external database dependency to keep the container footprint small and easier to reason about.Post-Quantum Encryption I use ML-KEM-768 for the encryption layer. Incoming mail is encrypted immediately using a client-generated public key and the plaintext is discarded. The server only ever stores encrypted message data and cannot decrypt it. I chose PQ because I wanted to build something I wouldn't have to revisit in five years. If it handles large PQ keys reliably, everything else is easy.Quick start: https://vaultsandbox.dev/getting-started/quickstart/Site: https://vaultsandbox.comI'd love feedback, especially on whether AGPLv3 would be a blocker for something you'd self-host in dev.
Enrichment
- Theme
- self-hosted infrastructure and security tools
- Vertical
- Horizontal
- Function
- Dev tools
- Audience
- Developer
- AI stance
- Not AI
- Project type
- Commercial product
- Normalized one-liner
- test email service integrations safely
- Manually corrected
- False
Could you build this?
Partial While standard web mocking is easy, a production-grade self-hosted SMTP server testing full TLS handshakes, custom DNS mocking, SPF/DKIM/DMARC validation, and zero-knowledge encryption requires deep email infrastructure knowledge.
What it would actually take: The architecture requires a custom low-level SMTP server (e.g. in Go or Rust) capable of acting as an MTA, handling raw TLS negotiations, and embedding full DNS/resolver mocking. It must implement robust RFC-compliant SPF, DKIM signature verification, and DMARC record evaluation libraries alongside an in-memory or containerized mail storage pipeline and REST/WebSocket APIs for CI runner inspection.
Discussion
14 comments analyzed.
Competitors mentioned: Mailtrap (email testing catch-all service), Twilio/SendGrid (email infrastructure), WeKan (kanban alternative mentioned for licensing context)
Concerns raised: AGPL license blocks corporate adoption due to GPL policies, GPL infection concerns with linked dependencies, Companies have blanket bans on GPL code in libraries, PII/sensitive data in dev/test email logs in regulated industries, Unclear if mock testing is sufficient vs real infrastructure testing
Feature requests: Support for application layer changes (template tweaks, provider switching, DNS updates), Commercial add-on backend with REST API integration, Modern licensing approach (FSL-1.1-MIT) for clearer paid license terms
Competitors
Other products that read as similar to this one — 149 launches clear the similarity bar, closest 8 shown.
Attention rank: #29 of 150 (itself plus its competitors, highest first — normalized so YC and Product Hunt are compared fairly).
Launched 68 days after the earliest competitor.
- Posthorn, self-hosted mail gateway · hn · 2026-05-27 · 83 upvotes · similarity 0.53
- Inbox Placement Test 2.0 · ph · 2026-09-29 · 1 upvotes · similarity 0.48
- mailQA — test every email your app sends · ph · 2026-09-10 · 1 upvotes · similarity 0.47
- Vault Mail · ph · 2026-09-22 · 2 upvotes · similarity 0.46
- SMTP Tunnel · hn · 2026-01-07 · 140 upvotes · similarity 0.45
- SmakMail · ph · 2026-09-15 · 1 upvotes · similarity 0.44
- CredMail · ph · 2026-09-14 · 1 upvotes · similarity 0.43
- Self-hosted email server for 2026 · hn · 2026-01-03 · 7 upvotes · similarity 0.41
Other launches for this product
- No other launches for this product.
Same idea, different domain
Nobody's really built a dev tools tool for Sales yet.