Force clients to use pgp encryption when sending email?

[dovecot at ptld.com]

> Basically I want the server to check if the message being sent is encrypted with OpenGPG and either proceed or reject the message based on that criteria.


Postfix is your submission service so i think best to look that direction. If there is a header you can check for (if the header exist then allow sending) then postfix has header checks regexp/pcre that would be simple enough to setup.

On the more complex side, postfix also supports policy servers you can write as a script (php, perl, python, etc) or you can go full on milter.


http://www.postfix.org/header_checks.5.html
http://www.postfix.org/SMTPD_POLICY_README.html
http://www.postfix.org/postconf.5.html#non_smtpd_milters