Hi, Our setup is as follows. We have an exchange server which forwards mail for particular domains to postfix for address rewriting. Postfix re-writes the sender domain address and forwards the mail down a private link. For example exchange sends mail to postfix with a sender address of [email protected] postfix rewrites the sender address as [email protected] and then forwards the mail. I have a need to rewrite the return path\address of all mail received from a pspecific address while still re-writing the sender domain as explained above before being forwarded by postfix. There are no local mailboxes on postfix. Postfix simple recieves mail re-writes the sender domain and forwards. Having read other posts I believe this can be done by using a different submission interface in postfix - but I have no idea how to do this. This is what I have seen on another site: The right solution is to use a different submission interface, that lets you set the envelope sender. For example: ( echo "EHLO $(uname -n)" echo "MAIL FROM:<com>" echo "RCPT TO:<org>" echo "DATA" echo "From: <com>" echo "To: <org>" echo "Reply-To: <com>" echo "Subject: the information you requested" echo "" perl -pe 's/^\./../' /some/path/to/msg-body echo "." echo "QUIT" ) | /usr/sbin/sendmail -bs Where in postfix would I create a new submission interface and is the above information the correct way to change the return path? Any and all help appreciated. Many Thanks