Distribution Group Expansion works for external users without any problems. However, federated users cannot IM a distribution group or see its members. Is this something that can be enabled?
I am using OCS R2 Std with ISA 2k6 and consolidated Edge.
DLExpansion requires Authentication in the Front End Server (on IIS), and since federated contacts, do not authenticate themselves, they do not have the ability to contact a Distribution Group.
This, I understand is by design, to prevent users on the internet from SPIM'ing your domain.