I would like to substitute message body with new one and *re-send* it to
somebody. I know it is quite basic but I have some problems with this.
The recipe I have:
:0 hw
| (formail -I"From: $MYADDR" \
-I"Subject: My subject"\
-I"To: $SMBD";\
echo "My new body";) | $SENDMAIL -oi $SMBD
Try piping to '$SENDMAIL -oi -t' instead of '$SENDMAIL -oi $SMBD'.