Create SDR rule in any mailserver

Introduction

This manual describes the general information for setting up a mail flow rule for Secure Direct Replies in any mail server. Please use the pages below for the specific instructions on:

1. Exchange Online
2. Exchange On Premise
3. Google Workspace

If your organization is using another mail server, please set up the routing as described below.

Mail routing logic

The logic (mail-server agnostic) should effectively be as follows:

• If: the References header of an email contains zivver-sdr-<your-Zivver-UUID>

There is no need to add the angle brackets (< >) that wrap the value in practice.

• Then:
  • Add the zivver-relay header with the value:
    • sdr → when using the Zivver Encryption Gateway.
    • smart-sdr → when using the Zivver DLP Gateway.
  • Route the message to smtp.zivver.com.
• Except if: the message headers contain the X-Zivver-Transport header.

This ensures that the IDD message itself — which also contains the SDR value in the References header — is not looped back to Zivver.

Updated on 2026-06-18