For Exchange on-premises environments (2013 or newer) without access to OWA, the Exchange Admin should follow the below steps to install Cirrus Insight on behalf of users.
Alternatively, if your Outlook users do have access to Office 365 or OWA, they can install with these steps: How do I install Cirrus Insight for Outlook?
1. In the Exchange Admin Center (EAC), navigate to Organization > Add-ins.
2. Click the New Add icon and then choose Add from URL.
3. Copy and paste the following URL in the URL field:
4. Click Install.
You may also need to allow/trust Cirrus Insight. Refer to IT Admins | How do I add Cirrus Insight to trusted/allowed lists?
Use the EAC to specify whether Cirrus Insight 2021 is available, enabled, or disabled.
5. In the EAC, navigate to Organization > Add-ins.
6. In the list view, select the Cirrus Insight add-in, and then click Edit.
If you want your users to be able to use Cirrus Insight, select Make this add-in available to users in your organization, and then select the option you want.
Optional, enabled by default: Use this setting if you want to allow your users to turn off Cirrus Insight.
Optional, disabled by default: Use this setting if you want to allow your users to turn on Cirrus Insight.
Mandatory, always enabled. Users can't disable this add-in: Use this setting if you don't want your users to turn off Cirrus Insight.
7. Click Save.
Exchange resources from Microsoft:
Updated Nov. 2021