If you're e-mailing people on the public internet, you're leaking your contacts and patterns of correspondence anyway, even if you're using end-to-end encryptio

If you're e-mailing people on the public internet, you're leaking your contacts and patterns of correspondence anyway, even if you're using end-to-end encryption. Even if you're outside the US, it's near impossible to ensure your traffic won't cross through US controlled infrastructure at some point. That said, Zimbra does all of what you're after, it's "freemium" open source (meaning that it's a commercial product with a free community edition) and it was fairly easy to deal with last time I set it up 4-5 years ago, presumably it's better now.