I am running a defederated local Matrix server, and I need to set up calls. From what I can tell, the "legacy" calls require a STUN and TURN server, and the new MatrixRTC standard seems to require them as well for Livekit to work. However, I do not want to expose anything out to the public internet, as I want everything to be behind NAT for local access only (all of the clients for the server will also be behind the NATted network). I also have Tailscale running on my servers, and it would be useful if I would be able to connect to the TURN server even when not in the network. Is there a way to get STUN/TURN to work in this situation? It seems that all the servers expect to have public network access.

I need to run my own email server for some of my domains, because the providers that I usually use don't support them (they use Unicode characters, and not everyone supports that yet). I have a small VPS that I run a few Docker containers on, and I'm wanting to try and run an email server on it as well. What containers are good for a low-hassle email setup? I don't need a mailbox webui (ex: roundcube), but it would be nice to have a UI for management. I do need multi-domain support, however.

EDIT: For anyone wondering, I decided to go with Mailu. Stalwart didn't play will with internationalized domains (although it was the only server to support EAI/SMTPUTF8), and Mailcow would have been a bit more difficult for me to change to bind mounts and reconfigure Docker networking with.