Procmail autoreply

I’ve got an autoreply script part in my procmail config.
It runs ok, but always bounces back from the SMTP server saying that there is no recipient specified, but looking at the headers of the bounced message, the correct To: header is there. Basicly, all I want it to reply with a modified subject, and a custom message prepended to the body. The pertinent part looks like this…

If anyone has done this, and can paste their code, it would be greatly appreciated.

:0 fhw # invert head
| formail -rk
-I “X-Class: Auth_Request_Sent”
-I “Precedence: junk (autoreply)”
-I “X-Loop: $LOOP_ID”
-I “From: $SENDING_ADDR” \

:0 afb # prepend file to body; note trailing space and hyphen

:0 ac
| $SENDMAIL -io -t