Contact Problems

Fix Cannot Add User as Distribution List Delegate in Exchange Online

Phi Hung Vo Oct 16, 2026 868 views

Question details

The user is unable to add specific individuals as delegates (Send As or Send on Behalf) to a distribution list in Exchange Online.

Fix: Cannot Add User as Distribution List Delegate in Exchange Online

Product: Exchange Online
Device & OS: not provided
Scenario: Attempting to assign delegate permissions to a distribution list for specific users via the modern Exchange admin center.
Observed behavior: The system fails to save the changes and returns errors such as 'Failed to update delegates at this time. Please try again later' or 'Object reference not set to an instance of an object.'

Before you start

Ensure you have Exchange Administrator or Global Administrator privileges, and verify that the target user has an active, mail-enabled mailbox before modifying permissions.

Solution 1Recommended

Assign Delegate Permissions via Exchange Online PowerShell

When the web-based Exchange admin center fails, using PowerShell often bypasses UI bugs and successfully forces the permission assignment.

The modern Exchange admin center sometimes struggles with specific recipient objects, causing time-out or update failures. Using the native PowerShell cmdlets directly is a reliable workaround to grant Send As and Send on Behalf rights.

Connect to Exchange Online

Open PowerShell as an administrator and run 'Connect-ExchangeOnline' to sign in with your administrator credentials.

Assign Send As Permission

Run the command: Add-RecipientPermission -Identity "YourDistributionListName" -Trustee "UserEmailAddress" -AccessRights SendAs

Assign Send on Behalf Permission

Run the command: Set-DistributionGroup -Identity "YourDistributionListName" -GrantSendOnBehalfTo @{Add="UserEmailAddress"}

Verify Permissions

Run 'Get-RecipientPermission -Identity "YourDistributionListName"' to confirm that the user has been successfully added to the delegate list.

Assign Delegate Permissions via Exchange Online PowerShell

Replication Delay: It may take up to 60 minutes for the new delegate permissions to fully replicate across Exchange Online and allow the user to send emails.

Solution 2

Validate the Recipient Object Properties

Determine if the specific user's account has underlying directory or property issues preventing the delegate assignment.

Free Microsoft Office alternative

Boost Your Productivity with WPS Office

While managing your Exchange Online settings, consider WPS Office for your daily document needs. It offers a lightweight, free alternative to Microsoft Office with excellent compatibility for your emails' attachments.

1. Download the Installer: Visit the official WPS Office website and download the free installation package for your operating system.
2. Install WPS Office: Run the downloaded installer and follow the simple on-screen instructions to complete the setup.
3. Open Your Documents: Launch WPS Office to instantly open, edit, and save your existing Microsoft Office files without formatting loss.

Free to use with comprehensive word processing, spreadsheet, and presentation toolsFully compatible with Microsoft Word, Excel, and PowerPoint formats (.docx, .xlsx, .pptx)Lightweight application that runs smoothly without overloading your systemFamiliar tabbed user interface for seamless migration from Microsoft Office

microsoft office alternative - wps office

Frequently Asked Questions

Why do I get a 'Failed to update delegates' error in Exchange admin center?

This error frequently occurs due to transient web portal glitches, backend replication delays, or hidden invalid properties on the specific user account being added to the distribution list.

What is the difference between Send As and Send on Behalf permissions?

'Send As' allows the user to send emails that appear exactly as if they came from the distribution list address. 'Send on Behalf' shows the sender to the recipient as 'User on behalf of Distribution List'.

How long does it take for delegate permissions to work after adding them?

After assigning the permission via the admin center or PowerShell, it typically takes between 15 and 60 minutes for Exchange Online to replicate the changes and allow the user to send emails successfully.

Can I add an external guest user as a delegate to a distribution list?

No, typically only internal, active mail-enabled users or shared mailboxes can be assigned Send As or Send on Behalf permissions for a distribution list in Exchange Online.

Outlook & Email Problems