Mail hosting is not that simple anymore. Your understanding of how it works is missing an entire world of complex issues that you need to solve outside of just hosting a mail server with an open SMTP port.

The biggest certainty is that just having an open port for an SMTP server dangling out there means you will 100% be attacked. Not just sometimes, non-stop. So you don't want to host on a machine with anything else on it, cuz security. So you need a dedicated host for that portion, and a very capable and restrictive intrusion detection system (let's say crowdsec), which is going to take some amount of resources to run, and stop your machine from toppling over.

Next, you need all your secondary record systems (SPF, DKIM, DMARC) pointing at a defined and unchanging record for your SMTP server, so you'll need a static IP. If you don't have that already, you're kind of SOL.

Next, you'll need to be running your own peer authentication system, then a spam filtering system (of which none of them work well without massive amounts of sample data, but you can use public lists to help block known bad actors), decent file threat scanning...you see where I'm going with this. It all takes a fair amount of resources, and even more if/when you get bad actors spamming the machine all the time.

Finally, you'll probably want this machine completely segmented from the rest of your network, which isn't really complicated, just costs a bit more money.

There's a reason why mail hosts and forwarding services cost money, and still exist. It takes a large amount of effort to be somewhat secure, or at least to best of your efforts. With the added costs associated with hosting your own mail servers, most people just avoid the hell out of it. I certainly wouldn't recommend it.

Have a look at https://forwardemail.net/. It's a service that handles accepting (and optionally sending) email on your domain, and forwarding any received mail to other backend services, like a gmail account. All you need to do is set some DNS records, like MX and their servers will handle everything. It works fine with domains hosted on cloudflare, and has excellent howto's to get everything set up and running.

Edit: The great thing about this service, imho, is their guides. They don't just have a static howto, they template in your information into the exact string you need to copy/paste into the service provider's web interface. Want to encrypt your plaintext TXT records? There's a button for that on the guide. Want to learn how to get around a port 25 ISP block, they have a guide for that. Want to set up proper Send-As from Gmail using their SMTP server? There's a guide for that. :-)

maybe a vpn provider that uses openvpn? advanced setup but you can have an openvpn client auto connect on boot and bind the mail and ddclient to the tunnel interface.

cloudflare has good support for ddclient, so when your IP changes updates are automatic.

Here's a good example of why I'm getting out of Gmail:

https://portswigger.net/daily-swig/encrypted-email-service-ctemplar-announces-closure

Since the government already has their sights on breaking them up, it would be a good idea to GTFO way before they implode:

I've found some interesting options here, but everyone wants to own your data. Just put it all in our servers, c'mon! It's free or low price, we're you centric and not as centric....

https://discuss.privacyguides.net/t/migration-away-from-gmail-to-another-free-service-with-imap/15297/2

Sure. But I want my stuff in my basement server and not in their basement server 😭.

Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread:

[Thread #924 for this sub, first seen 18th Aug 2024, 19:55] [FAQ] [Full list] [Contact] [Source code]

In the end, I want to have my emails self hosted from my house. Meaning that I can go to my local computers or my phone locally or remotely to the mailu interface, I can send and receive emails using my user1@mysite.com email and none of that email ends up on a Gmail or protonmail server stuck there forever. I can't download all my Gmail to Thunderbird on my computer because then my phone would not have access to it. So to me that just means that I need to host the email server at home, but how to safely access it is the ideal solution.