A DID is pointed to a 'ring all' group of four extensions. At night, 3 of the extensions are normally put in DND, leaving 1 member of the group available.

When the remaining member is on a call, the next caller to the DID goes to the overflow destination (voicemail) even though that extension has plenty of group intercom buttons available that the call could appear on.

Can this group be programmed to allow multiple calls to a 'busy' extension?