https://code.google.com/p/gpg-mailgate/ gpg-mailgate is a gateway for Postfix that uses the GNU Privacy Guard application to encrypt e-mails before being sent to the next hop. INSTALLATION: Ensure that GPG is installed and configured. Make sure public keys for all of your potential recipients are available in the GPG home directory you use in step 2 Configure /etc/gpg-mailgate.conf based on the provided sample config Place gpg-mailgate.py in /usr/local/bin/ Place the GnuPG directory in /usr/local/lib/python2.5/site-packages Add the following to the end of /etc/postfix/master.cf gpg-mailgate unix - n n - - pipe flags= user=nobody argv=/usr/local/bin/gpg-mailgate.py 127.0.0.1:10028 inet n - n - 10 smtpd -o content_filter= -o receive_override_options=no_unknown_recipient_checks,no_header_body_checks -o smtpd_helo_restrictions= -o smtpd_client_restrictions= -o smtpd_sender_restrictions= -o smtpd_recipient_restrictions=permit_mynetworks,reject -o mynetworks=127.0.0.0/8 -o smtpd_authorized_xforward_hosts=127.0.0.0/8 Add the following to /etc/postfix/main.cf content_filter = gpg-mailgate Restart postfix.