---
summary: Connecting your mail platform to ScaiLine and keeping it running.
order: 5
title: Operating
path: operating
status: published
---

# Operating

ScaiLine signs mail where your mail already flows. Pick the page for your platform:

* [Postfix and the milter](operating/postfix-milter): grommunio, Mailcow or your own Postfix.
  The message never leaves your server.
* [Microsoft 365](operating/microsoft-365): Exchange Online sends outgoing mail through the
  hosted ScaiLine relay and receives it back signed. Currently in preview.

Whatever the platform, two rules hold: ScaiLine never holds up mail (when in doubt, a message
goes out without a signature), and you can always switch it off with one change on your side.