KoltrixDocs

FAQ

Can I switch from Postmark, Resend or Mailgun?

Yes. It is usually a day's work.

  1. Add your domain and publish its DNS records. If your domain already has an SPF record for your current provider, Koltrix shows a merged record that allows both, so you can switch gradually. The MX record moves your domain's incoming mail to Koltrix, so publish it when you're ready.
  2. Add the addresses you send from to the domain.
  3. Change the API call. POST /api/v2/emails takes from, to (an array), cc, bcc, subject, body_html and body_text. See Sending email. Or point your SMTP settings at the relay.
  4. Bring your suppression list. Add the addresses under Settings → Blocked senders → We won't email these.
  5. Move your webhooks. Koltrix signs them differently; see Webhooks.

Check the "Current limitation" notes on those pages against what your integration relies on, such as attachments or BCC.

How is Koltrix different?

Transactional email services send your application's mail and stop there. Koltrix also gives your team the inbox where the replies land, on the same domain, with the same suppression list and the same message log. A customer who replies to a receipt reaches a person, and that reply is counted on the message.

How much does it cost?

Plans and prices are on koltrix.com/pricing. New workspaces start with a free trial, no card needed. Each plan's limits are in Limits and quotas.

Where is my data?

Koltrix runs on OVHcloud servers in Frankfurt, Germany, in the European Union. There is no choice of region today. The details are in the privacy policy and the list of subprocessors.

Koltrix is not SOC 2 or HIPAA certified. If you need a certification, ask before you sign up.

Does Koltrix's AI send email?

No. Koltrix's AI features summarise, sort and draft, and the AI assistants connection lets tools like Claude read and organise your mail and save drafts. None of them can send, forward or permanently delete a message; a person always clicks Send.

You can't bring your own AI provider key today.

Is the API stable?

/api/v2 is the stable, public API, and it's what these docs describe. Changes to it add things; they don't change or remove existing fields and behaviour without a new version and notice. Changes are listed in the Changelog.

The app talks to Koltrix through other, internal endpoints. Don't build on those: they change without notice.

Can I belong to more than one workspace?

Yes. Switch between them from the workspace menu in the app. API keys belong to the workspace they were created in, and an AI assistant connection belongs to the workspace you chose when you approved it.

Is there an SDK?

Not yet. The API is a few JSON endpoints, and examples for cURL, Node.js, Python, Go and PHP are in Sending email.

What does Koltrix do for deliverability?

  • Signs every message with your domain's own DKIM key.
  • Suppresses addresses that hard-bounce or unsubscribe, across everything you send.
  • Adds unsubscribe links and headers to broadcasts and sequences.
  • Paces sending from new domains.

The rest is your DNS and your list. See Deliverability and suppressions.

My question isn't here

Email [email protected]. We answer within one business day.