We would like every one to have an e-mail member list of external customers (to be BCC'ed) but that list may need to be modified in the future at any given notice. It would be preferable for this list to be contained within MSOutlook, and without the need to distribute local copies every time a change is made. Is this possible within the GAL considering these customers are external (they don't have AD accounts). Are there any alternate solutions?
You can create a new AD group (distribution list), and populate it with external addresses, which will appear in the GAL.