**Just notice that I’d an unpublish post (was saved under draft for some reason) and I’m now officially republishing it.

On a recent deployment, a customer of mine had file a complaint that they were not able to expand the distribution group within the Lync Client. So when I search through the distribution groups within the Active Directory, the object does exist; from Exchange, the emails are distributed correctly.

So I decided to look it from the Lync Server; from the Event Viewer, an event was logged:

An unhandled exception was encountered in Service service.

Exception Details. System.Exception: Multiple enteries found for Group@domain.com at Microsoft.LiveServer.ThrowSoapFault(Exception.E) at Microsoft.LiveServer.DLExpansion.Service.QueryADGetDistributionListInfo(string mail, DirectorySearcherdSearcher) ….

With this information, I did a quick search on the same SMTP address that notice that another ‘group’ existing with the same SMTP address – it was actually the Security Group that causes the conflict when searching for the distribution group. Resolution to this was to modify the SMTP addresses at the Security Group and restart the Front-End Service.

I’d to make sure that the Address Book Service rebuilds the correct information and the users were able to download the latest update – with that, the mystery has been solved. *Whew*