Show Hn: Vaultsandbox – Test Your Real Mailgun/ses/etc. Integration (2026)

Keep your provider and your config. Just swap the recipient to validate real TLS, DNS, and SPF/DKIM entirely inside your VPC.

Deploy VaultSandbox with a single Docker Compose file. Auto-provisions TLS and DNS.

You mock the email client to get a green build. But in production, you use real SMTP, real TLS, and real DNS. This disconnect creates a dangerous blind spot.

No TLS, DNS, or MX records — a fantasy environment.

Flaky CI tests relying on sleep(5) break pipelines.

SPF, DKIM, and DMARC only break on real domains. Mocks always pass.

SSL/TLS issues surface only in production once you disable checks in dev.

HTML emails render differently in real clients vs. plain text viewers.

VaultSandbox provides isolated inboxes that behave exactly like production — without exposing a single byte of customer data.

Infrastructure requirements: Public IP, ports 25/80/443 open.

Source: HackerNews