Use the regexp engine since we have one

core/postfix/conf/outclean_header_filter.cf

@@ -1,14 +1,8 @@
 # This configuration was copied from Mailinabox. The original version is available at:
 # https://raw.githubusercontent.com/mail-in-a-box/mailinabox/master/conf/postfix_outgoing_mail_header_filters
 
-/^\s*Received:[^\n]*/	IGNORE
-
-# Remove other typically private information.
-/^\s*User-Agent:/        IGNORE
-/^\s*X-Enigmail:/        IGNORE
-/^\s*X-Mailer:/          IGNORE
-/^\s*X-Originating-IP:/  IGNORE
-/^\s*X-Pgp-Agent:/       IGNORE
+# Remove typically private information.
+/^\s*(Received|User-Agent|X-(Enigmail|Mailer|Originating-IP|Pgp-Agent)):/	IGNORE
 
 # The Mime-Version header can leak the user agent too, e.g. in Mime-Version: 1.0 (Mac OS X Mail 8.1 \(2010.6\)).
 /^\s*(Mime-Version:\s*[0-9\.]+)\s.+/  REPLACE $1