Hello, I'm currently setting up a somewhat unique personal email server. I have a local server (Raspberry Pi) and a remote server (VPS running OpenBSD). Emails are sent to the remote server and are then relayed to my local server. When I send an email it goes from my local server to the remote server, and is then relayed to it's recipient. Mostly I've got it all working how I want it to.
While I'm aware that nothing stored on a VPS (even momentarily) is completely safe, I'd like to make my remote email server as secure as possible from prying eyes (for example if my VPS host or a hacker made a snapshot of my server for maleficent purposes). Most of the time messages should only be on my remote server for a matter of seconds at most before being sent to my local server, but if my local network is down they could remain there much longer. Also as the queue is written to disk someone could recover old messages from deleted queues. The three areas I'm looking at so far are: 1) OpenSMTPD queue encryption This is a good step, but presumably the key is stored in memory, so could be retrieved from a snapshot of the server. Maybe I could automate the key to change from time to time? 2) OpenBSD disk encryption I read in a forum post that OpenBSD disk encryption only stores a part of the key in memory at any one time. I can't find anywhere else that says this, and I can't work out how that'd be possible. 3) GPG message encryption I could in theory set up something that takes inward messages out of the queue (before they are written to disk), encrypts them with my public key, and then enters them back into the queue. But for most outward messages GPG encryption won't be an option. I'd appreciate your opinions and any advice. Sincerely, Josey
