imap_append

$stream = imap_open("{your.imap.host}INBOX.Drafts","username", "password");

$check = imap_check($stream);
print "Msg Count before append: ". $check->Nmsgs."\n";

imap_append($stream,"{your.imap.host}INBOX.Drafts"
                   ,"From: me@my.host\r\n"
                   ."To: you@your.host\r\n"
                   ."Subject: test\r\n"
                   ."\r\n"
                   ."this is a test message, please ignore\r\n"
                   );

$check = imap_check($stream);
print "Msg Count after append : ". $check->Nmsgs."\n";

imap_close($stream);