---
title: "Opensense Outlook Add-in integration with GCC High environments"
slug: "opensense-add-in-integration-with-gcc-high-environments"
description: "Deploy the Opensense Outlook Add-in in Microsoft 365 GCC High: requirements, the custom manifest, the GCC High directory sync tool, and proxy allowlisting."
updated: 2026-06-30T12:55:13.000Z
canonical: "https://help.opensense.com/docs/opensense-add-in-integration-with-gcc-high-environments"
---

> ## 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.

# Opensense Outlook Add-in integration with GCC High environments

## Overview

Opensense supports deployment in Microsoft 365 Government Community Cloud (GCC) High environments. These are isolated, non-routed environments designed for federal agencies and organizations that handle sensitive government data. The Outlook Add-in deploys differently in GCC High than in standard commercial Microsoft 365.


## Requirements

<dl class="kb-insights-summary">
  <div><dt>Exchange Online or Microsoft 365</dt><dd>Version 2104 (Build 13929.20296) or later, with API v1.10 support.</dd></div>
  <div><dt>Modern Authentication</dt><dd>Must be turned on, for secure communication.</dd></div>
  <div><dt>Custom manifest</dt><dd>The add-in is deployed with the GCC High-specific manifest URL.</dd></div>
  <div><dt>Azure AD enterprise application</dt><dd>Used for directory synchronization in the isolated environment.</dd></div>
</dl>


## How GCC High deployment differs

Unlike standard commercial Microsoft 365 environments, GCC High needs:

1. **Custom add-in deployment.** Deploy the add-in manually in the **Add-ins** section of the Microsoft 365 admin center, with a GCC High-specific manifest file, instead of through the standard **Integrated Apps** portal.
2. **A dedicated directory sync tool.** A specialized Azure AD enterprise application, the Opensense GCC High Directory Sync tool, syncs directory information securely within the isolated GCC High environment.
3. **Portal configuration.** In the Opensense portal, turn on the **Office 365 GCC High** toggle, so that routing and authentication work correctly.
4. **Proxy allowlisting.** If your organization uses a web proxy, such as Zscaler, allowlist the Opensense domains that the add-in needs.


:::note[Mobile add-ins are off by default]
In GCC and GCC High environments, mobile add-ins are disabled by default. Administrators may need to change tenant settings with Exchange Online PowerShell to turn them on. See [Outlook mobile add-ins in GCC and GCC High environments](https://help.opensense.com/docs/using-the-outlook-mobile-add-in-within-gcc-environments).
:::


## Getting help with deployment

GCC High deployments are specialized and have strict security requirements, so Opensense provides dedicated implementation support. For help with your GCC High deployment, contact your Opensense representative or [help@opensense.com](mailto:help@opensense.com).

## What's next

- [Outlook mobile add-ins in GCC and GCC High environments](https://help.opensense.com/docs/using-the-outlook-mobile-add-in-within-gcc-environments): turn on mobile add-ins.
- [Allowing Opensense traffic through your network proxy or firewall](https://help.opensense.com/docs/opensense-proxy-firewall): the domains to allowlist.
- [Outlook Add-in supported environments](https://help.opensense.com/docs/supported-environments-for-the-opensense-outlook-add-in)