This space has been a bit wooly for a while, with a fair bit of confusion abounding, however Microsoft have cleared things up nicelly with 19 (you heard right) new certifications and more coming.
Check this out:
The new generation of certifications is actually good news for Exchange administrators. In earlier versions of Exchange you passed a single administration or design exam to achieve the Microsoft Certified Professional credential. However, passing both the administration and design exams did not qualify you for a higher certification level unless you also happened to achieve MCSA (Microsoft Certified Systems Administrator) and/or MCSE (Microsoft Certified Systems Engineer) status. Even then, the Exchange messaging certifications were tacked on as a qualifier to MCSA/MCSE to indicate your area of specialization. Both the MCSA and the MCSE are centered on Windows and Active Directory administration and design. To obtain that MCSE: Messaging certification and let the world know that you are a highly-qualified messaging administrator you actually had to pass eight separate exams.
With the new generation of certifications, there are two levels of Exchange certification: Technology Specialist and IT Professional. Granted, this makes for some really long certification names, but they clearly identify your area of expertise. There are three exams in the Exchange Server 2007 certification track.