Keyboard-first email, AI that summarizes and drafts for you, and shared workflows so your team moves as one. Try free, no card required.
Just finished the migration audit — all DNS records validated, SSL chains intact. I ran the replay suite for 4 hours and saw zero inconsistencies.
Ready to flip production Friday morning. Suggest 9am PT — traffic is at its lowest and SRE is on standby.
Trusted by teams at fast-moving companies
Send, receive, broadcast, and measure — under one auth, one dashboard, one bill.
Receive, reply, search, and label across every domain you've verified. Each tenant lives in its own Postgres schema — switching is one click, zero data crossover.
Per-key permissions, idempotency, auto-retry. Point any mail library at smtp.koltrix.com:2525.
Lists, segments, drip sequences, A/B subjects, double opt-in, one-click unsubscribe.
Auto domain warm-up, DKIM via Rspamd, hard-bounce suppression, rep monitoring.
HMAC-SHA256 for sent · delivered · bounced · opened · clicked. Replayable from the UI.
Every entry and exit point is a well-known wire format — no proprietary SDK to learn.
OpenAPI-described JSON over HTTPS. SDKs for any language with HTTP.
Point your existing mail library at smtp.koltrix.com:2525 and authenticate with your API key.
HMAC-SHA256 signed, replayable, idempotent. Any HTTPS endpoint you control.
Every inbound email walks six well-defined stops. No black boxes, no magic.
Steps Resolve and Store are your data — bound to your tenant's own schema. Every step is independently retried with backoff. Outbound mail walks the same path in reverse.
Sending email shouldn't mean stitching together a transactional API, a newsletter tool, an inbox, and an analytics dashboard — and paying for the seams.
Koltrix is one product, one auth, one bill — one source of truth for every message your business sends or receives.
Stay on the free tier while you validate. Pay when the volume justifies it.
Start free. 100 sends/day on the Free plan. No credit card required.