Can't assign Send on Behalf permissions for shared mailboxes in the EAC

Symptoms

When you sign in to the Exchange Admin Center (EAC) in Microsoft Exchange Server, you see limited options to set the permissions of a shared mailbox. The option to individually manage the Send on Behalf permissions is available for user mailboxes. However, only the option to manage full mailbox permissions is available for shared mailboxes.

Cause

This issue occurs because the Send on Behalf permission can't be managed in the EAC.

Workaround

To work around this issue, add the Send on Behalf permission by using the following Set-Mailbox PowerShell command:

Set-Mailbox -Identity <MailboxOrGroupIdentity> -GrantSendOnBehalfTo <Delegates>

For example, to assign the Send on Behalf permission for Sean Chai's mailbox to the delegate Holly Holt, run the following command:

Set-Mailbox -Identity seanc@contoso.com -GrantSendOnBehalfTo hollyh

Note

If you use Microsoft 365, you can use the Microsoft 365 admin center to assign the Send on Behalf permission to shared mailboxes.