diff --git a/postfixd.sh b/postfixd.sh
index bb653cb..058ae26 100755
--- a/postfixd.sh
+++ b/postfixd.sh
@@ -16,6 +16,8 @@ case $1 in
     if test -n "${SRS}"; then
       postconf -e sender_canonical_maps=tcp:${SRS}:10001
       postconf -e recipient_canonical_maps=tcp:${SRS}:10002
+      postconf -e sender_canonical_classes=envelope_sender
+      postconf -e recipient_canonical_classes=envelope_recipient,header_recipient
     fi
 
     test -n "${NETWORKS}" && postconf -e mynetworks="${NETWORKS}"