As already mentioned several times, selfhosting a mail server is not recommended unless you're particularly interested in hosting a mail server, but with that said, you might find this project interesting:
If you need to throw in the towel on email self-hosting, don't be ashamed. Mail servers are one of the more difficult projects to run. If you do end up outsourcing this, I recommend SendGrid, it's reliable and free.
I followed the setup guide, did everything in the DKIM, DMARC and SPF documentation page. The initial setup required more involvement from me than your standard docker-compose self-hosting deployment, but I got no issues at all (for now, fingers crossed) after the initial setup : I never missed any inbound e-mails, and my outbound e-mails have not been rejected by any spam filter yet.
However, I agree with everyone else that you should not self-host an important contact address without proper redundancy/recovery mechanism in case anything goes wrong.
You should also understand that self-hosting an email address means you should never let your domain expire to prevent someone from receiving emails sent to you by registering your expired domain. This means you should probably not use a self-hosted e-mail to register any account on services that may outlive your self-hosted setup because e-mail is frequently used to send password reset links.
I used nixos-mailserver with success, and very little configuration. Most of it was dns, and thr guide walked me through it. You would have to a nixos box somewhere though. I spun one up on my vps for it.
If you do self host I suggest reading carefully the Gmail guidelines for mails. They are the leaders in the field and they dictate the level of security required.
DNS forward and reverse, DKIM, SPF, DMARC, ARC, DANE, bounce signature etc. Email is indeed a very complicated thing to host. I work on emails system all day and and I wouldn't host my own mail.
Even worse I'm hoping email disappear and another technology takes it place. Emails are unreliable and outdated, they need to go.
I agree with everyone here that self-hosting email is never easy, but if you still decide to go down this route then here are two tips that I personally found very helpful, especially when you decide to host it at home:
The first is to get an SMTP relay server. That's just another mail server that yours can log into to actually send its mail, just like an email client would. That way you don't have to worry about your IP's sending reputation, because everyone will only see the relay's reputable IP.
Second is to configure a Backup MX. That's an additional MX DNS entry with lower priority than the primary, and it points to a special mail server that accepts any mail for you and tries to deliver it to the primary server forever (or something like an entire week). So when your primary server is unreachable other sending servers will deliver mail to the backup, and it delivers the mail to the primary as soon as that's back online.
You can get these as separate services, but some DNS providers (like Strato for example) offer both with the base domain package. It makes self-hosting an email server much simpler and more reliable in my experience.
I I agree with everybody else saying that the email server should not be self-hosted. But I have a specific exception to this rule, which I was keen to try, but I never did this or take this with a pinch of salt.
I do self-host on my services, but at the moment I keep myself hosted email on a public server, not on my home server.
Since I am using a tunnel to access my services from outside, my home server is actually using my public server ip. moving my email self-hosting to my home server would not actually change the front facing IP address of that email server, and no harm would be done to my mail server.
But is it really worth it? Probably not. Since I would still need some kind of backup email server out on the internet for the rare situations where my home server is cut from the internet due to power outage or ISP being down.
You want full reliability for your email server. So your home connection without UPS or backup connection isn't going to cut the cheese fully.
So, I would suggest you don't self-host your email on your home server. You can still self-host your email, but on a public server. Be aware, though, that is a difficult task which will require lots of effort and many months to get it done right and accepted everywhere.
I host my own mail. When it's down, the mail just gets delivered after I get online again. Almost all mail servers are configured to retry over a period of several days before giving up.
Once my health insurer sent me mail by post to tell me that my mail server was down. That was kinda funny.