If you feel like doing this yourself, get something like a Raspberry Pi 3 (or better, like the Asus Tinker Board) and use sovereign (from github) to automatically install your own mail server/owncloud on it.
Then get a dirt cheap VPS (less than $15/yr) from lowendbox/lowendtalk and run a OpenVPN tunnel.
So what's the advantage of having this at home instead of an ISP?
For one, backup and restore is fast and easy. You can use your NAS that's at home. You may want to have an additional offline backup in case your home network gets completely compromised.
A box at home is also more difficult to tamper with. If you're paranoid, put it into a tamper resistant box.
Unfortunately reputation management is a requirement nowadays for all senders of MTA. And it's an ongoing hassle.
Helm promises to handle this in a way that doesn't let them read transmitted mails. You still have to trust them ultimately, but the stakes are higher.
Then get a dirt cheap VPS (less than $15/yr) from lowendbox/lowendtalk and run a OpenVPN tunnel.
So what's the advantage of having this at home instead of an ISP? For one, backup and restore is fast and easy. You can use your NAS that's at home. You may want to have an additional offline backup in case your home network gets completely compromised. A box at home is also more difficult to tamper with. If you're paranoid, put it into a tamper resistant box.