Another solution is to use for example Ciphermail to automatically encrypt mail server-side. In this way you don't need to reject non-encrypted mail, you can just make sure it gets encrypted before it leaves premises.
-----Ursprungligt meddelande----- Från: dovecot-bounces@dovecot.org dovecot-bounces@dovecot.org För Austin Witmer Skickat: den 8 december 2021 07:15 Till: dovecot@ptld.com; dovecot@dovecot.org Ämne: Re: Force clients to use pgp encryption when sending email?
Thanks for that info! It’s just what I needed!
On Dec 7, 2021, at 8:35 PM, dovecot@ptld.com wrote:
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