On a computer that is running Microsoft Exchange Server 2007 server, the
IMAP SEARCH command does not
support a CHARSET argument. If you use the IMAP protocol to send a
SEARCH
command that has the CHARSET argument, you may receive the following error
message on the Exchange 2007 server:
"BAD Command
Argument Error."
However, based on RFC 3501, the response should
be "NO" instead of "BAD" if the CHARSET argument cannot be recognized. Because
of this problem, some IMAP based third-party applications do not work correctly
with Exchange 2007 Server.