Koltrix
Startups
Transactional, Lifecycle or Marketing? Classifying SaaS Emails
Every SaaS email falls into one of three buckets, and the bucket decides consent, unsubscribe links and how it's sent. Practical definitions and the gray areas.
4 min read
GuidesHow to audit a messy shared inbox in one afternoon
An hour-by-hour runbook for cleaning up a neglected shared inbox: take stock, clear the noise, rescue waiting threads, fix labels, and add three useful rules.
4 min read
DeliverabilityTLS-RPT: get told when inbound TLS fails
SMTP TLS Reporting (RFC 8460) sends you daily JSON summaries of failed TLS sessions. How to publish the record and read the reports that come back.
5 min read
GuidesMigrating Aliases, Groups and Shared Mailboxes Without Losing Mail
User mailboxes get migrated. Aliases, groups and catch-alls get forgotten, then mail bounces. How to map every address before cut-over and test it after.
4 min read
Customer supportRefund and billing emails: templates and judgment calls
Copyable reply templates for duplicate charges, forgotten cancellations, partial refunds and failed payments, plus guidelines on when to refund without debate.
5 min read
Email APISMTP relay vs HTTP API: how should your app send email?
SMTP relays are universally compatible; HTTP APIs are easier to make idempotent and observable. Compare them on errors, retries, security and speed.
4 min read
StartupsMapping Every Lifecycle Email Your SaaS Sends
Most SaaS teams can't list every email their product sends. How to run an inventory, what to record for each message, and the problems it usually uncovers.
5 min read
Team inboxLabels vs folders for team email: a practical taxonomy
Labels let a thread carry several tags; folders force one place. A worked example of building a label taxonomy for a six-person SaaS team, with naming rules.
5 min read
DeliverabilityWhy transactional email lands in Gmail Promotions
Receipts and alerts in the Promotions tab are usually a content and stream problem. The signals Gmail likely uses and changes that tend to help.
4 min read
ComparisonsResend, Postmark and SendGrid: Choosing a Transactional API
Three of the most common answers to how should our app send email, compared fairly: who each one suits, where each is strongest, and the questions to ask first.
5 min read
AI & emailAI email agents: which tasks are safe to delegate today
A decision table for AI email agents: rate sorting, summarizing, drafting, sending and deleting on reversibility and blast radius, then decide who acts.
5 min read
ProductHow Koltrix makes send retries safe
Why the Koltrix send API claims an Idempotency-Key before queuing anything, what each response code means and how to retry from your client.
5 min read