remailer exposing sender

I am concerned about a the security of using a remailer such as remailer@soda.berkeley.edu. My concern is that after an anonymous message has been sent or posted. Someone could then send a message to the sender using the encrypted address supplied by the remailer. This message which is sent back through the remailer could be composed of known text which then could be traced back to the originator system of the anonymous sender. Any comments would be appreciated. thanks, tom