Not much point. Save yourself the 2GB and put it elsewhere.
http://support.microsoft.com/default.aspx?scid=kb;%5Bln%5D;815372

On a heavily loaded Exchange server (more than 300 - 400 active users -
mailboxes being used at any given time), I usually tell people to go ahead
and spec out 4GB, but 3GB is about the limit for most servers.  In addition
to what Mark posted, remember there are other things running on the Exchange
server.  The system attendant can gobble up a few hundred MB of RAM as can
the inetinfo process (on a busy server).  Plus, I saw some servers just the
other day that were using about 3.5GB of their available RAM thanks to
Symantec Mail Security's over enthusiastic use of memory (it is a RAM hog).

However, anything over 4GB is a profound waste of money when configuring an
Exchange server, IMHO.

If you have a server with more than 1 GB of RAM, get to know the /3GB
/USERVA=3030 switches for the BOOT.INI.  And, avoid the /PAE switch on
Exchange servers.  It does NOT do any good.