My reply:
A BIS user's interaction with their email has NOTHING to do with Exchange or the 'Send As' patch that is now available from Microsoft. This patch ONLY affects BES users that are using Exchange 2000/2003 as their mail platform. The BIS user's reply-to address never will touch an Exchange environment - you could use
![[email address]](?emailimage=068d4f7e0ba30d0d4a5a088e47184fee)
as your BIS reply-to address and not have a single issue as it would NEVER touch Microsoft's mail servers.