Koltrix
Guides
Estimating Transactional Email Costs as You Grow
A practical method for forecasting how many transactional emails your product will send per month, and what that volume will cost as your user base grows.
4 min read
Customer supportMeasuring customer satisfaction in email support
How to measure satisfaction with email support: CSAT timing and wording, reading comments, response bias, signals beyond surveys, and keeping pay out of it.
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
StartupsWaitlist and Beta Invite Emails That Keep Momentum
A waitlist goes cold faster than founders expect. The confirmation, update and invite emails that keep people interested until you are ready to let them in.
4 min read
Team inboxSignatures and tone for shared mailboxes: a team agreement
Personal or team sign-off? What goes in a signature? How five people sound like one team? A FAQ for agreeing on signatures and tone in shared mailboxes.
4 min read
Email APITransactional HTML that renders everywhere: the constraints
Email clients support a narrow, quirky slice of HTML and CSS. The constraints that matter for receipts and alerts, and a structure that survives them.
4 min read
GuidesPer-User vs Per-Workspace Email Pricing: Doing the Math
Per-user and per-workspace pricing look similar at three people and diverge fast after that. A worked way to compare the two models for your own team size.
4 min read
GuidesEvery DNS record a sending domain needs, in one table
A reference table of the DNS records a domain that sends email should have: MX, SPF, DKIM, DMARC, MTA-STS, TLS-RPT and BIMI, with syntax for each.
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
ComparisonsIntercom or Email-First Support? Picking a Channel Strategy
Live chat and email-first support set different expectations and need different staffing. How to choose a channel strategy, with a fair look at Intercom.
4 min read
GuidesHow to triage an email backlog after time off
A runbook for your first morning back: filter to mail that involves you, read threads newest-first, batch-archive the noise, and reply to the few that matter.
4 min read
DeliverabilitySPF flattening: when it helps and when it breaks mail
Flattening replaces includes with IP ranges to dodge the lookup limit. Here is how it works, why it rots, and safer alternatives like subdomains.
5 min read