Article ID: 2841150 - View products that this article applies to.
Consider the following scenario:
The recipient "MailboxName" is already a member of the group "GroupName".
This issue occurs because of a logic defect in the ECP code. Specifically, ECP calls only the Update-DistributionGroupMember cmdlet instead of calling the Add-DistributionGroupMember or Remove-DistributionGroupMember cmdlet for large distribution groups.
To resolve this issue, install the following update rollup:
(http://support.microsoft.com/kb/2866475/ )Description of Update Rollup 2 for Exchange Server 2010 SP3
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
Article ID: 2841150 - Last Review: August 13, 2013 - Revision: 1.0