The problem with AUTH is that you need to create the auth string (encoded). The commands are:
<BR>
HELO your domain
<BR>
AUTH authmethod
<BR>
send auth string
<BR>
MAIL FROM: email
<BR>
RCPT TO: email
<BR>
DATA
<BR>
all the data
<BR>
<CRLF>.<CRLF>
<BR>SEND
<BR>
QUIT
Try it and let me know if it works works!!!. I think that perhaps is easier make a java program that get each mail, check and the forward it using for example java mail api (I allready do that).