We are currently an Exchange 2003 domain that synchronizes with an Exchange 2007 installation using SimpleSynch for the GAL and InterOrg for Free-Busy. The one-way trust is that we trust them. We are a university and they are a hospital.
We are upgrading to Exchange 2007 soon, and need a replacement strategy for both the functions above. I have settled on either keeping SimpleSynch (as both parties have a license) or going to IIFP and GAL Synch. It's the Free-Busy replacement that is giving me a hard time. It is my understanding that Exchange 2007 does not support InterOrg, except when dealing with an Exchange 2003 installation.
What can I use as a replacement for this, bearing in mind that the best I will be able to do, in terms of trusts, is the one-way that exists now.