⚠️ Sideloading should only be used when installing from Microsoft AppSource is not an option. Sideloaded installs do NOT receive automatic updates — you must manually reinstall the add-in each time a new version is released. Monitor the Release Notes to stay current.

This article covers two sideload methods: a single-user manual install for end users, and an organization-wide deployment via PowerShell for IT admins.

Section 1 — End User: Manual Sideload

Use this method if you are an individual user who cannot install ExtendSync from the Microsoft AppSource store. Always check with your admin first.

Manifest File URL

Download the manifest file from the URL below.

Production Manifest URL:

https://manifests.ceol.cloudextend.app/olns-production.xml

Step 1 — Remove Any Existing Version

Before installing, remove any previously installed version to avoid conflicts.

Go to https://aka.ms/olksideload — the Add-Ins for Outlook window will open.
Select My Add-Ins.
Locate any existing ExtendSync add-in, click … in the lower-right corner of the tile, and select Remove.

Reference: Microsoft — Delete add-in from Outlook

Step 2 — Install from Manifest File

Go to https://aka.ms/olksideload and select My Add-Ins.
Scroll down to Add a Custom Add-in → choose Add from File.
Select the downloaded production manfiest file from above.
A warning prompt may appear — click Install and wait for completion.

📘 The Add from URL option is no longer available in Outlook. Download the file from the URL first, then use Add from File.

✅ ExtendSync is now installed. Remember: this install will not update automatically.

Reference: Microsoft — Install Custom Add-Ins

Section 2 — IT Admin: Organization-Wide Deploy via PowerShell

Admins familiar with Powershell can use this method to deploy ExtendSync across multiple users or your entire organization when AppSource is not available. Requires Exchange Online admin access.

We have sourced these instructions from Microsoft. See their article for the most up to date instructions.

⚠️ Because this is a sideloaded install, updates will NOT be pushed automatically. You must remove the old version and redeploy each time CloudExtend releases a new manifest. Monitor Release Notes for any updates.

If you have questions about sideloading apps via PowerShell please reach out to Microsoft directly.

Prerequisites

Microsoft 365 Global Admin credentials
PowerShell (Windows PowerShell or PowerShell 7+)
O365CentralizedAddInDeployment module — install with: Install-Module -Name O365CentralizedAddInDeployment

Manifest File URL

Version	Manifest URL
Production	https://manifests.ceol.cloudextend.app/olns-production.xml

Step 1 — Install and Import the Module

# Install the Centralized Deployment module

Install-Module -Name O365CentralizedAddInDeployment

# Import the module

Import-Module -Name O365CentralizedAddInDeployment

Step 2 — Connect Using Admin Credentials

# Connect to the Centralized Deployment service

Connect-OrganizationAddInService

# A sign-in prompt will open — enter your Global Admin credentials

📘 You must use Global Admin credentials. The sign-in prompt opens automatically after running Connect-OrganizationAddInService.

Step 3 — Deploy the Add-In

Deploy ExtendSync from the manifest file. You can optionally assign users directly during deployment using the -Members parameter.

# Deploy from a downloaded manifest file (assign to all users)

New-OrganizationAddIn -ManifestPath 'C:\path\to\olns-production.xml' -Locale 'en-US'

# OR deploy and assign to specific users immediately

New-OrganizationAddIn -ManifestPath 'C:\path\to\olns-production.xml' -Locale 'en-US' `

-Members 'user1@domain.com','user2@domain.com'

Step 4 — Get the Add-In Product ID

After deployment, retrieve the ProductId — you will need it for all subsequent management commands.

# List all deployed add-ins and find ExtendSync

Get-OrganizationAddIn

# Or get full details for all add-ins

foreach($G in (Get-OrganizationAddIn)) {

Get-OrganizationAddIn -ProductId $G.ProductId | Format-List

}

Step 5 — Configure Availability

Use Set-OrganizationAddIn to enable or disable the add-in, and Set-OrganizationAddInAssignments to control which users have access.

# Enable the add-in (replace <ProductId> with value from Step 4)

Set-OrganizationAddIn -ProductId <ProductId> -Enabled $true

# Assign to all users in the tenant

Set-OrganizationAddInAssignments -ProductId <ProductId> -AssignToEveryone $true

# OR assign to specific users or groups

Set-OrganizationAddInAssignments -ProductId <ProductId> -Add `

-Members 'user1@domain.com','sales@domain.com'

# Remove specific users from access

Set-OrganizationAddInAssignments -ProductId <ProductId> -Remove `

-Members 'user1@domain.com'

📘 Changes may take up to 24 hours to propagate to all users in your organization.

Useful Management Commands

Command	Purpose
Install-Module O365CentralizedAddInDeployment	Install the required PowerShell module
Connect-OrganizationAddInService	Connect using Global Admin credentials
New-OrganizationAddIn	Deploy a new add-in from a manifest file
Get-OrganizationAddIn	List all deployed add-ins and retrieve ProductId
Set-OrganizationAddIn	Enable/disable an add-in or update its manifest
Set-OrganizationAddInAssignments	Assign or remove users and groups
Remove-OrganizationAddIn	Permanently delete a deployed add-in
Get-Help <cmdlet> -Full	View full help for any cmdlet

Updating to a New Version

Because we don't have a way of knowing if a user has sideloaded the add-in admins will need to check the release notes that are emailed to them to see if a new manifest is available (not all updates require a manifest update).

Since sideloaded installs do not auto-update, follow these steps whenever CloudExtend releases a new manifest:

Check the Release Notes for the updated manifest URL and download the new file.
Get the ProductId of the existing deployment:

Get-OrganizationAddIn

Update the add-in manifest in place using Set-OrganizationAddIn:

Set-OrganizationAddIn -ProductId <ProductId> `

-ManifestPath 'C:\path\to\new-olns-production.xml' -Locale 'en-US'

💡 You can update the manifest in place with Set-OrganizationAddIn rather than removing and redeploying. This preserves your existing user assignments.

Troubleshooting

Issue	Resolution
Add-in not appearing after PowerShell deployment	Allow up to 24 hours for propagation. Ask users to restart Outlook.
'Add from URL' option missing in Outlook	This option has been removed by Microsoft. Download the file and use Add from File instead.
Warning prompt when sideloading	Expected for custom add-ins. Click Install to proceed.
Multiple versions showing in Outlook	Remove older versions via https://aka.ms/olksideload before reinstalling.
'Connect-OrganizationAddInService' not recognized	Run Install-Module and Import-Module steps first, then retry.
Access denied when connecting	Ensure you are using Global Admin credentials, not a standard admin account.
Add-in stopped working after a CloudExtend update	A new manifest has been released. Check the Release Notes and update using Set-OrganizationAddIn with the new manifest file.

Still Having Trouble?

• 💬 Chat: Click the chat icon at the bottom-right of the CloudExtend Help Center.

• 📧 Email: cloudextend-support@celigo.com

When contacting support, please include:

• Your NetSuite role name

• A screenshot of any error message

• The installation method attempted and steps already tried

For Admins and IT Teams

For organizations that prefer to sideload or manually deploy the current production version of ExtendSync for Outlook, follow the steps below.

📘 READ ME FIRST

Although sideloading is available, we recommend installing the ExtendSync add-in from the Microsoft Office Store or via Centralized Deployment for automatic updates and easier management.

To stay up to date with the latest manifest file and sideload instructions, regularly monitor the Release Notes for any updates or changes.

Installing the Production Add-in

Installing or reinstalling the production add-in involves removing any existing version (such as an older or preview build) and then adding the latest production version using the manifest file URL.

Step 1: Remove the Existing Version

Before installing or redeploying the production version, uninstall any previously installed add-in (e.g., an older build or preview release).

You can always reinstall the latest production version later from the Microsoft Office Store.

Go to https://aka.ms/olksideload, and the Add-Ins for Outlook window will open.
Select My Add-Ins.
Locate the old or preview versions of ExtendSync add-in, click ... in the lower-right corner of the add-in tile, and select Remove.

Reference: Microsoft Article - Delete add-in from Outlook

Step 2: Install the Production Version using Manifest File

ExtendSync Outlook Manifest URL: https://manifests.ceol.cloudextend.app/olns-production.xml

Download the file from URL: https://manifests.ceol.cloudextend.app/olns-production.xml
From the Add-ins for Outlook screen, select My Add-Ins.
Scroll down to Add a Custom Add-in → choose Add from File.

Note: The Add from URL option is no longer available to install a custom Outlook add-in. As a workaround, open the URL in your preferred browser to download the add-in file, then use the Add from File option to install it.