---
title: "How does Opensense work with Microsoft 365?"
slug: "how-does-opensense-work-with-office-365"
description: "Opensense works with Microsoft 365 through Exchange Online mail flow rules and the Outlook Add-in. Covers deployment methods and add-in requirements."
updated: 2026-03-20T18:12:11.000Z
canonical: "https://help.opensense.com/docs/how-does-opensense-work-with-office-365"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://help.opensense.com/llms.txt
> Use this file to discover all available pages before exploring further.

# How does Opensense work with Microsoft 365?

## Overview

Opensense integrates with Microsoft 365 through Exchange Online mail flow rules and the Opensense Outlook Add-in. Together, they let Opensense manage email signatures centrally across your organization, so every outbound email carries a consistent brand, the required legal text, and your marketing campaigns. User data comes from Azure AD (Entra ID) or another connected directory, and syncs to Opensense to fill in each signature.

## How the integration works

Opensense connects to your Microsoft 365 environment through two components:

<dl class="kb-insights-summary">
  <div><dt>Mail flow rules in Exchange Online</dt><dd>A transport rule routes qualifying outbound emails to Opensense. Opensense applies the correct HTML signature and any configured marketing banners, then returns the email to Microsoft through TLS for final delivery. Opensense adds a custom header to each processed email, so that it is not processed again.</dd></div>
  <div><dt>Opensense Outlook Add-in</dt><dd>A Microsoft 365 Integrated App, deployed through Centralized Deployment. It loads automatically when a user opens a compose window in Outlook. Depending on the configuration, it removes local signatures, inserts the Plain Text Block token, or shows a Visual Preview in compose. For server-side methods, the add-in pane also shows a preview of what recipients will receive.</dd></div>
</dl>

Mail flow rules control where and how signatures are applied. The add-in controls the compose window experience. The combination you use depends on your deployment method.

<figure class="kb-media-frame"><div class="kb-media-frame__visual"><img src="https://help.opensense.com/media/m365-arch-5-e6cfa5e3a11a.jpg" alt="Opensense O365 architecture diagram: email from the sender goes to Office 365 in Azure Cloud; when the body contains [[#]] and the X-SG-Signature header is not present, it is routed over TLS to the Opensense Smarthost, which adds the X-SG-Signature header and returns the email to Office 365 with TLS client certificate authentication for delivery to the recipient" width="1600" height="900" loading="lazy" decoding="async"></div><figcaption><strong>Opensense M365 architecture</strong> · Office 365 routes qualifying email through the Opensense Smarthost</figcaption></figure>

## Deployment methods

Opensense supports three deployment methods for Microsoft 365. Each one decides how signatures are applied, what users see in compose, and which compliance and marketing capabilities are available.

<ul class="kb-test-methods" role="list">
  <li>
    <span class="kb-test-methods__label">Server-side, after send</span>
    <strong>Stamping</strong>
    <p>Opensense applies the signature entirely server-side after the email is sent. Nothing is inserted into compose.</p>
    <ul>
      <li>The add-in pane shows a preview of what recipients will receive</li>
    </ul>
  </li>
  <li>
    <span class="kb-test-methods__label">Recommended</span>
    <strong>Plain Text Block</strong>
    <p>The add-in inserts a token into compose. A mail flow rule routes the email to Opensense for server-side transformation.</p>
    <ul>
      <li>The add-in pane shows a preview of what recipients will receive</li>
      <li>Opensense's patented approach, recommended for most deployments</li>
    </ul>
  </li>
  <li>
    <span class="kb-test-methods__label">Client-side, in compose</span>
    <strong>Visual Preview</strong>
    <p>The full HTML signature is rendered client-side in the compose window.</p>
    <ul>
      <li>Users can see and edit the signature before sending</li>
    </ul>
  </li>
</ul>

:::note[Choosing a method]
For the tradeoffs of each method and guidance on choosing one, see [Comparing Outlook Add-in deployment methods](https://help.opensense.com/docs/deployment-mode-comparison).
:::

## Outlook Add-in requirements

<dl class="kb-insights-summary">
  <div><dt>Mailbox</dt><dd>Exchange Online. On-premises Exchange does not support the add-in.</dd></div>
  <div><dt>License</dt><dd>A Microsoft 365 or Office 365 subscription. Volume licenses (Office 2016, 2019, 2021) do not support the required API version.</dd></div>
  <div><dt>Deployment method</dt><dd>Centralized Deployment through the Microsoft 365 Admin Center.</dd></div>
  <div><dt>Outlook for Windows</dt><dd>Version 2104 (Build 13929.20296) or later, Click-to-Run only. MSI-based installs are not supported.</dd></div>
  <div><dt>Outlook for Mac</dt><dd>New Outlook, version 16.38.506 or later. Legacy Outlook for Mac is not supported.</dd></div>
  <div><dt>Outlook on the web (OWA)</dt><dd>Supported in modern browsers with an M365 mailbox.</dd></div>
  <div><dt>Outlook Mobile (iOS and Android)</dt><dd>Supported. GCC and GCC High environments need additional PowerShell configuration to <a href="https://help.opensense.com/docs/using-the-outlook-mobile-add-in-within-gcc-environments">enable mobile add-ins</a>.</dd></div>
  <div><dt>Office JavaScript API</dt><dd>Version 1.10 or later. Some features need version 1.13 (M365 subscriptions only).</dd></div>
  <div><dt>Admin consent</dt><dd>Recommended before launch, to prevent per-user permission prompts.</dd></div>
  <div><dt>Propagation</dt><dd>Allow up to 72 hours after deployment for the add-in to appear for users.</dd></div>
</dl>

## On-premises Exchange

Organizations that run on-premises Exchange are supported through ExSBR by MessageConcepts, a transport agent installed directly on the Exchange servers. This is a separate integration path. The Outlook Add-in is not supported in on-premises Exchange environments. ExSBR licensing is separate from Opensense and is passed to the customer. Setup is completed with an Opensense implementation engineer. To discuss your requirements, contact [help@opensense.com](mailto:help@opensense.com).


## What's next

- [Outlook Add-in overview](https://help.opensense.com/docs/outlook-add-in-overview-1)
- [Comparing Outlook Add-in deployment methods](https://help.opensense.com/docs/deployment-mode-comparison)
- [Outlook Add-in supported environments](https://help.opensense.com/docs/supported-environments-for-the-opensense-outlook-add-in)
- [Scoping Outlook Add-in users in the Microsoft 365 admin center](https://help.opensense.com/docs/clone-outlook-add-in-scope-users-for-opensense-in-m365-admin)
- [Microsoft 365 integration overview (change request)](https://help.opensense.com/docs/change-request-office-365-integration-with-opensense): the connectors and transport rules in detail.