Linux – Encrypting a file name in linux

For a specific inbox, this is easy enough to do with procmail. Here's a link to get you started.

The problem is if you want to do this to all incoming emails. That, too, could be done, but it's a little more involved due to trying to determine the correct public key for each recipient. If you want to encrypt with the same key for all messages, then it gets easier.

However, as someone else said, if you want to do wholesale encryption, I'd resort to partition-level encryption, which is an entirely different (and much more involved) discussion .

More specific requirements and your desired goal would be helpful to provide you with an answer.

If you want to encrypt your outgoing mail using GnuPG, without involving your PHP code, then GNU Anubis might be what you are looking for. It can sit in-front of your SMTP server and (among other things) apply GnuPG encryption to your mails.

The potential issue here is that Anubis both accepts and submits mail using SMTP. While there obviously isn't any problem with using SMTP to pass the mails along to Postfix, PHP tend to use the local sendmail binary. One possible solution, which I haven't tried myself, is to point PHP:s sendmail_path= toward the Anubis helper script msg2smtp.pl

Of course, if there's multiple Postfixes involved, one on your web server as well as one on your companies designated mail server, then there really isn't any problem. In that case all you have to do is simply plug Anubis in between.