Hi Jan,
As per the doc I linked above, this seems to be a requirement for MWI & GDM's;
GDMs
MWI for GDMs is done in the same manner as MWI for personal mailboxes. If the extension associated with a GDM appears on a phone, then that phone receives MWI for message activity in the GDM. MWI for GDMs is not done to the phones associated with the extensions of the group's members; it is done only to the extension directly associated with the group mailbox.
GDMs can be associated with extension types that cannot be placed as button appearances on a phone, such as Cisco CME automatic call distributor (ACD) or hunt-group pilot numbers. If the GDM is associated with such a type of extension, there is no MWI for messages in that GDM on any of the phones that belong to the ACD or hunt group. You can work around this by configuring the ACD or hunt group to forward calls to an intermediate extension (which is set permanently to CFA calls to the voice mail pilot number), rather than forwarding directly to voice mail. The intermediate extension can now be placed on a phone as a button appearance and MWI for GDMs can be implemented even for GDMs functionally assigned to ACD or hunt groups.
Cheers!
Rob
