We will soon be standing up exchange 2010 SP2 along with a partner running the same version. We will be using some kind of GAL sync so mailboxes in the partner org show up in our GAL, I am guessing as Contacts. The problem is we don't want our GAL flooded with 10's of thousands of entries as this will be confusing for users. We want separate GALS for each org and each user on our side must be able to select which GAL they want when sending an email. At this time, I am not concerned about the other Org. Since we have far less users, they will probably do nothing. Basically, our GAL should be the default and if they want to send to the other Org, they can select that GAL in Outlook. I was reading up on ABP but I am not sure if that is what I want here because it appears you can assign only on ABP per mailbox and we don't want to restrict users from accessing a GAL. We just want them separated. What is the best way to do this?