MAILATTACH This program starts a process which listens on the LOOPBACKv4 address for incoming connections from postfix. The postfix master should view this as an advanced filter as explained in their documentation for post queue filtering: http://www.postfix.org/FILTER_README.html The original attempt was to implement this as a pre queue filter, but this required the milter protocol and postfix currently does not implement the replace body function from libmilter. You can specify the following command line options: --abort-pgp --noabort-pgp To either abort the attachment process if PGP encryption or signatures have been detected or not. If true, the mail will not be modified. --abort-dkim --noabort-dkim To either abort the attachment process if DKIM signatures have been detected or not. If true, the mail will not be modified. --in-port -i The incoming smtp port/the port from which mail is received. --out-port -o The outgoing smtp port/the port to which mail ist passed through. HOWTO We essentially are MITM sniffing your email traffic and playing proxy from your postfix to your postfix. That's how this is intended to work according to the postfix website. This program needs to be started via it's own systemd service on system boot. You need to add the in and oputput ports to your postfix queue as described in the link above. More documentation is to a TODO