It rather depends on what you mean by “encrypted email provider”. Proton don’t do anything magical, incoming emails arrive unencrypted and they just encrypt them for storage. Likewise, outgoing emails may be stored encrypted, but aren’t encrypted on the recipients end. In both cases the email is unencrypted at the remote party’s end.

If you want encrypted email between you and someone else the solution is GPG encryption. It’s not too complicated to set up, but does involve both parties using it, so you’re probably not going to get your bank on board, for instance, but it works between friends. The other big advantage is that it works with any email provider, “encrypted” or not. The very nature of email means that the headers need to remain plaintext so that the mail can be routed, but even proton can see those on incoming or outgoing mails.

Contrary to popular consensus, I’d say that hosting your own mail infrastructure isn’t too difficult if you are willing to make certain compromises. Hosting incoming mail is a case of deploying one or more SMTP servers that can only receive email for your domain and store it on an IMAP server. All these components are well documented (I like postfix for SMTP and Dovecot for IMAP). Register these servers as the MX records for your domain, and you have incoming email. Spam filtering is a separate issue to look into, but quite doable. Outgoing mail is slightly more tricky, but there are various well trusted SMTP relays you can use for that. I have used Amazon’s SES service successfully, and I’m looking at SMTP2Go, as they seem to have a free tier that woud be well suited to a personal email setup. Remember, the incoming and outgoing servers do not need to be the same, which seems to be what trips a lot if people up. You do need the appropriate SPF and DKIM records for the outgoing servers on your domain though.