VaultSandbox

A self-hosted SMTP server for testing app email with real TLS, DKIM checks, spam scores and simulated delivery failures.

vaultsandbox.com

Visit vaultsandbox.com ↗would rather buy than build

Running since2026Launch year from the maker

Details

What it does: Transactional email, Developer tools
Who it’s for: Developers, Software companies
Extras: Can self-host
Works with: sendgrid, postmark, amazon ses
Tags: email testing, smtp sandbox, ci testing, dkim validation, chaos testing

SendStreak
Sits between your app and SES, Postmark, Gmail or SMTP to add templates, retries, logs and routing without switching provider.
Free plan · Transactional email · Developers
Mailsac
Gives developers and QA testers throwaway and private inboxes they can read by API to test signup and reset emails.
Free plan · Developer tools · Developers
EmailJS
Lets developers send templated email from browser or app code through their own mail provider, without writing a server.
Free plan · Transactional email · Developers
DebugMail
A hosted test SMTP server that catches emails sent from development environments so teams can inspect and share them.
Free plan · Developer tools · Developers