Koltrix
Startups
Plain-Text vs Designed Emails for SaaS Lifecycle Mail
Plain text feels personal and renders everywhere. Designed HTML suits receipts and digests. Which lifecycle emails belong in which format, and why.
4 min read
Customer supportSupport inbox burnout: workload practices that help
How to spot support inbox overload early, rotate the hardest work, protect focus time, cap concurrent threads and use AI drafts without removing human judgment.
4 min read
Email APIDesigning a transactional email API you will not regret
Decisions that make an email-sending API pleasant for years: async acceptance, idempotency, explicit errors, stable fields and a clean event model.
4 min read
ProductCustomer Loop: Where Replies to Your Receipts Should Go
Customers reply to receipts and password resets all the time. Customer Loop threads those replies into your team inbox under the message that caused them.
5 min read
GuidesHow to plan for email volume spikes
A playbook for predictable spikes like launches and price changes and sudden ones like outages: what to prepare, how to triage the rush, and what to review.
5 min read
DeliverabilitySeparate subdomains for transactional and marketing mail
Splitting streams across subdomains contains reputation damage. How to structure them, align SPF and DKIM per subdomain, and what it cannot protect.
4 min read
GuidesSending Lifecycle Emails From Your Own Job Queue
For founders who code: build onboarding and trial emails with an events table, a scheduled job and an email API, with idempotency and suppression built in.
5 min read
AI & emailHow AI reads long email threads, and where it slips
Quoted history, signatures, context limits and who-said-what confusion: how AI models process long email threads, why summaries go wrong, and how to help them.
5 min read
GuidesMTA-STS from scratch: DNS record, policy file, testing
Set up MTA-STS for inbound mail: the _mta-sts TXT record, the HTTPS policy file, testing mode, then enforce, plus the mistakes that break delivery.
5 min read
StartupsReactivating Dormant Paid Accounts Before They Cancel
Some customers keep paying but stop logging in. How to spot dormant accounts, what to send the admin, and why offering a downgrade can save the relationship.
5 min read
Team inboxArchive or delete? Retention habits for team mailboxes
Why archiving customer mail usually beats deleting it, what is safe to delete, how to handle attachments and storage, and how to write a retention policy.
5 min read
Email APIObservability for email pipelines: logs, metrics, traces
Trace a message from API call to SMTP response. What to log, which metrics to emit and how to correlate IDs so 'did it send?' takes seconds.
4 min read