The Best Practice Analyzer of Exchange gives the following error in SBS 2008:
Disable MAPI clients warning:
Some versions of MAPI clients are blocked on server SERVER.server.local. Verify that version '6.x.x.x' and version '8.x.x.x' clients are not blocked as the Microsoft Exchange System Attendant process uses these version identifiers for performing server functions. Current MAPI blocking setting: 0.0.0-5.3164.0.
I shall appreciate if some link for resolving this problem is provided.