Now, I know this is ugly but it works for me on an Exchange 5.5 server. This comes from a web interface to our excehange server that I wrote a few years back.

    $imapp = Mail::IMAPClient->new(    Server      =>    'servername,
                                       User        =>    'userid',
                                       Password    =>    'password',
                                       Uid         =>    1,
                                       Debug       =>    0
                                  );
    $tempuid = $imapp->append_string("Sent Items", $messagestring ,"\\
+Seen");
    $tempuidarray->[0] = $tempuid;
    $imapp->set_flag("\Seen",$tempuidarray);
    if(!$tempuid){warn "ERROR saving to sent items: $@\n"; }
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I'm sure that Exchange 2003 is quite different from 5.5 but I would hope that IMAP is still IMAP. I don't know what LAMP is so I apologize if my reply seems ludicrous.