Koltrix
Startups
Make Onboarding Emails Replyable and Read Every Answer
Onboarding emails that invite a reply turn automation into conversations. How to ask the right question, route replies to a real inbox, and use what people say.
5 min read
AI & emailWriting a style guide your AI drafts can follow
A one-page style guide template for AI-drafted email: voice, banned words, formatting, sign-offs, and the policies a model must never invent on its own.
5 min read
DeliverabilityA staged path from DMARC p=none to p=reject
A week-by-week DMARC rollout: monitor with p=none, fix every legitimate source, move to quarantine, then reject, with clear exit criteria per stage.
4 min read
ComparisonsAmazon SES vs a Managed Email API: Trade-Offs for Small Teams
Amazon SES is famously inexpensive per message. A managed email API costs more and does more for you. How to weigh price against engineering time.
4 min read
Customer supportGetting reproducible bug reports by email on the first try
What to ask when a customer emails about a bug, how to ask without a wall of questions, what to check yourself first, and a reusable request snippet.
4 min read
DeliverabilityWhy DMARC breaks mailing lists, and how ARC helps
Forwarders and mailing lists modify messages and break SPF and DKIM. Understand the failure, From rewriting, and what ARC chains do and do not fix.
4 min read
GuidesSwitching Transactional Email Providers With Zero Downtime
Moving your app's email to a new provider doesn't need a risky big-bang cut-over. Dual DKIM, a thin sending interface, gradual rollout and suppression export.
4 min read
Team inboxAuto-label rules that stay maintainable after a year
Why email rule sets rot and a checklist to prevent it: one purpose per rule, clear names, a documented why, testing on real mail, and quarterly pruning.
4 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
StartupsFounder-Signed Emails: When a Personal Note Beats a Template
A short note from the founder can do what no template can, if it's honest and the founder reads the replies. When to send one, when not to, and how to write it.
4 min read
AI & emailHuman-in-the-loop patterns for email automation
Five ways to keep a person in control of email automation, from approve-to-send to sampled audits, with guidance on which pattern fits which kind of task.
4 min read
GuidesSMTP enhanced status codes (RFC 3463), decoded
Enhanced status codes like 5.1.1 and 4.7.0 say why delivery failed. Learn the class.subject.detail structure and the codes you will see most often.
5 min read