Centos 7, Webmin/Virtualmin up-to-date
:0 * ^From.*firstname.lastname@example.org * !^FROM_DAEMON * !^FROM_MAILER * !^X-Loop: email@example.com | (formail -rt \ -A "X-Loop: firstname.lastname@example.org" ; \ echo "Testing";\ echo "This is an automated response";\ echo "Not sure to see your message";\ echo "So please try again tomorrow" ) | $SENDMAIL -t -oi
An incoming mail from email@example.com to firstname.lastname@example.org accomplishes the first condition and the automated response is sent to email@example.com but the original mail is lost, it is not delivered to $HOME/Maildir/cur as usual.
It is a long story of tests and log checks.
Summary: Postfix delivers incoming mail to Procmail. Procmail executes the recipe but does not deliver the original mail to inbox directory