Koltrix
Guides
Testing email locally with a fake SMTP server
Point your app at a local SMTP catcher during development to see every message without risking real delivery. Setup, workflow and what it cannot test.
4 min read
DeliverabilityInbox placement testing: seed lists, panels and limits
Seed tests show where a message lands for test accounts, not for your users. What seed lists and panel data can tell you and how to use them honestly.
4 min read
AI & emailRed-teaming your AI inbox setup with safe test emails
Send yourself harmless test emails with embedded instructions to see if your AI assistant obeys mail content. Test cases, expected behavior and a scoring sheet.
5 min read
Email APITesting transactional email in CI without real sends
Assert on the message your code builds, not on an inbox. Layered tests for transactional email: rendering units, contract tests and a few end-to-end checks.
4 min read
GuidesTesting SMTP by hand with swaks and openssl
Talk to a mail server directly to see what it really says. Use swaks and openssl s_client to test auth, TLS, relaying and rejections step by step.
5 min read
GuidesKeeping staging environments from emailing real customers
Copying production data into staging is how customers get test emails. Use allowlists, recipient rewriting and separate credentials to make it impossible.
4 min read