Hi, I recently set up my own email server

• It's a huge pain in the ass getting things like DMARC and DKIM and whatever to work. Without those, most providers won't even deliver your messages. But luckily, there are websites that help you check and fix your configuration
• Even once you do get these things set up correctly, most providers will send your outgoing messages straight to the recipient's spam folder
• That being said, I believe most providers will mark you as "not spam" if the other person initiates the conversation. So this could be a non-problem if you're making an email for your business and putting it on business cards or something.
• Mullvad (VPN provider) self-hosts their support email, and they seem to be doing fine.

Hope that helps