You can register for 70-237: Designing Messaging Solutions with Exchange 2007 as of today, should you be so inclined. 70-237's little buddy 70-238 is scheduled to release on June 28, 2007. The combo of MCTS: Exchange Server 2007 (via 70-236) + 70-237 + 70-238 = an MCITP: Enterprise Messaging Administrator credential.