[Question] Does anyone run their own email server?

Yes, I still run my own email server. It is not for the faint of heart, but once it's configured and your IP reputation is clean, it's mostly smooth sailing. I have not had any deliverability problems to date, initial setup/learning period notwithstanding.
If you're not scared away yet, here are some specific challenges you'll face:
SMTP ports are typically blocked by many providers as a spam prevention measure. Hosting on a residential connection is often a complete non-starter and is becoming more difficult on business class connections as well (at least in the US, anyway).
If you plan to host in a VPS, good luck getting a clean IPv4 address. Most are on one or more public blacklists and likely several company-specific ones (cough Microsoft cough). I spent about 2 weeks getting my new VPS's IP reputation cleaned up before I migrated from the old VPS.
Uptime: You need to have a reliable hosting solution with minimal power/server/network downtime.
Learning Curve: Email is not just one technology; it's several that work together. So in a very basic email server, you will have Postfix as your MTA, Dovecot as your MDA, some kind of spam detection and filtering (e.g. SpamAssassin), some kind of antivirus to scan messages/attachments (e.g. Clamd), message signing (DKIM), user administration/management, webmail, etc. You'll need to get all of these configured and operating in harmony.
Spam prevention standards: You'll need to know how to work with DNS and create/manage all of the appropriate records on your domain (MX, SPF, DMARC, DKIM records, etc). All of these are pretty much required in 2023 in order for messages from your server to reach your recipient.
Keeping your IP reputation clean: This is an ongoing challenge if you host for a lot of people. It can only take one or two compromised accounts to send a LOT of spam and land your IP/IP block on a blacklist.
Keeping up with new standards: When I set my mail server up, DMARC and DKIM weren't required by most recipient servers. Around 2016, I had to bolt on OpenDKIM to my email stack otherwise my messages ended up in the recipient's spam folder. -Contingency Plan: One day you may just wake up and decide it's too much to keep managing your own email server. I'm not there yet, but I've already got a plan in place to let a bigger player take over when the time comes.
- Yep. I’ve hosted my own mail server since the early oughts. One additional hurdle I’d add to you list is rDNS. If you can’t get that set up, you’ll have a hard time reaching many mail servers. Besides port blocking, that’s one of the many reason it’s a non-starter on consumer ISP.
  I actually started on a static ISDN line when rDNS wasn’t an issue for running a mail server. Moved to business class dsl, and Ameritech actually delegated rDNS to me for my /29. When I moved to Comcast business, they wouldn’t delegate the rDNS for the IPv4. They did create rDNS entries for me, and they did delegate the rDNS for the IPv6 block. Though the way they deal with the /56 IPv6 block means only the first /64 is useable for rDNS.
  But, everything you list has been things I’ve needed to deal with over the years.
  
  Yeah, I totally forgot about reverse DNS. Good catch. I probably left out a few other things what with the repressed trauma of it all. lol.
  I had to deal with Suddenlink business, and they were (somehow) surprisingly worse than what you described for Comcast (I didn't know that was possible, TBH). Suddenlink wouldn't even unblock the SMTP ports at all let alone delegate rDNS to our static.

It’s a great learning exercise but challenging to get right and ensure your deliverability and basically impossible from a residential-grade IP address (if you have a business class static IP at home you could pull it off).
I ran an email server for decades but gave in and pay to host my email now.
If google decides you’re a bad guy it’s such a pain to crawl back from that and I prefer my email to just work.

It's bad out there when it comes to hosting your own email server. This blog post shows somebody's experience in detail, and it's worth reading. https://cfenollosa.com/blog/after-self-hosting-my-email-for-twenty-three-years-i-have-thrown-in-the-towel-the-oligopoly-has-won.html
It's all so sad.
- That was a sobering read. We all feel victorious when we see big tech fail after they wronged their users, but fundamental technologies that actually run the world have already been lost, and may never be recoverable for egalitarian use.

Despite my willingness to self-host almost everything, e-mail remains the last frontier for me. Keeping abreast of standards, keeping up today, avoiding implications in abuse and many, many smaller issues abound ... and that's despite my fixed IP and ISP willing to set up a reverse-DNS for me.
Instead I've gone with a paid email provider that I'm REALLY happy with.

Hosting a mail server is really easy. Making sure Hotmail, Gmail and others accept your emails is a nightmare.
I don't host my own email, I just delegate my email management to a small provider.
- I am learning this is the case. I think I may be better off running a Nextcloud instance, or similar suite using better applications for stuff like file sharing, which is more important.
- I am learning this is the case. I think I may be better off running a Nextcloud instance, or similar suite using better applications for stuff like file sharing, which is more important.
- I am learning this is the case. I think I may be better off running a Nextcloud instance, or similar suite using better applications for stuff like file sharing, which is more important.

I host my own mailserver, and to be honest it's pretty painless. Usually I just let it run without giving it any thought. It's on rare occasions that I need to put a bit of work into improving the inbound spam scanning.
Selfhosting does need quite some knowledge of the software stack and several additional protocols to set them up correctly to get your outgoing email delivered. Also, like already mentioned in another comment, you absolutely need an IP address from a non-blacklisted subnet (I think most VPS providers will be okay, residential definitely not).
My software stack: Arch Linux (soon NixOS), Postfix, Dovecot, rspamd, opendkim, opendmarc.
Additional techniques configured: SPF, DKIM, DMARC, DNSSEC.
As you can see it's quite a lot, and I've been doing for more than 20 years now, so my opinion can be a bit skewed. I'd say go for it if selfhosting is a hobby.
- I have been learning about it, and what really has motivated was seeing my current provider ProtonMail have an anniversary sale, and just having the least affordable pricing just to get a couple features I need. I have never been a fan of cloud storage, I have never needed an online service to handle my calendars or whatever else.
  I need to do do this out of principle.
  You are right, that is a lot of software in use. However, I have been given a lot of recommendations. I got my own domain name. I am almost ready. I just need to setup a few more things. I am taking a long time to do this, I got distracted with other self-hosted applications, but I do want to try running a mailserver.

Not worth the hassle - best compromise is to get your own domain but use a provider like fastmail to host it.
If they turn sour you can move your domain to another mail host.
- I think this is the solution I was thinking about in the first place. I was just musing about it being part of a home lab. I have to consider whether this solution is is better than just paying for secure email.
  
  There are advantages to having your own domain - you can use something like vendor8832@yourdomain.com so each site you sign up to gets their own unique "to" address, that way you can easily send their mail to trash when you dont' need to deal with them anymore, and will also let you know what company had a data breach if that unique email address starts to get spam.

Just take a look at https://docs.mailcow.email/
This runs from a small box with everything included. It gives you all the tools and config needed for running a secure and feature rich email service. Webmail, some sort of exchange emulation, webcalender on top of a solid postfix/dovecot install with rspamd as spam filter. Everything is configurable via a nice web UI.
After 15y running my own mail service and editing a lot of config files, I use this piece of free and open software and find it very good. All you need is a box somewhere in the internet. Running from a homelab will instantly fail, expect you have a static ip.
- Neato! There seems to be a lot of solutions for running a mail server.
  Yeah, I think it is time, I need to get familiar with Docker.
  Yeah, I was clueless thinking I could run it from my home. Hah. I just wanted to avoid paying for a VPS. Which is silly because I buy too much crap all the the time and have multiple subscriptions.
  This is actually valauable.
  
  mailcow lists a small german vps hoster with a fair price and the right sizing. It's not a big hoster, gmail and microsoft are not blocking the ip-range and the ASN is not listed on any blacklist.
  The support is quick and helpful, rDNS was a matter of minutes to set up. You don't need any deeper knowlegde of docker, since it is a one-time job to set the things up und get the stack running. The documentation of mailcow is very good.
  You can run it from home, but you will need a forward host like sendgrid and maybe a backup mx. You can set a primary ip and a backup ip wich will get all the mails when the primary host is down. I guess, there a comercial or free backup-mx services out there. No problem. If you have a static ip for your homelab or at least a dynamic dns-name, it will work. Recieving is easy. But you will need a good forward-service for sending.

I used to run my own mail server about 2 years ago but unfortunately the spam got so bad I didn't have the time to manage all the filters. I moved over to ProtonMail since I can still use my own domain there. So I guess I would say it's not really worth it also it really sucks if your power is out and not having access to sent your power company a strongly worded email.

I'm using openbsd with dovcot, opensmtpd on a pi. I used mailhardener to get it scoring well. I've had no issues with it getting flagged.

I want to do a setup where i use mailcow at home for receiving emails but Amazon ses SMTP for sending, it's possible? Looks like it is, but i didn't investigate it

Nope. It can’t really be self hosted anymore, as having a residential IP is a straight track to the spam folder. It can be done if you also pay for a mail relay service, but then what’s the point of self hosting when you need to rely on a cloud service anyways.

Obligatory PSA: ProtonMail isn't any more secure than Gmail and is likely a honeypot scheme crafted by government agencies: https://encryp.ch/blog/disturbing-facts-about-protonmail/
I know the title of that sounds clickbaity, but they cite their sources. It's worth the read for those curious about ProtonMail's history and their CEOs.
- Tbh, that document reads like a discovery channel 2am aliens documentary, but it's not completely without merit.
  There are a couple line items about software services they're using that are shitty that sound pretty legit. The fact that they're operating in locations where they might have to hand over data sounds pretty legit. Their warrant compliance and logging/handing over a person's IP address is legit.
  The CIA honeypot stuff is all really circumstantial. If the CIA was in as deep as is claimed, a lot of the real evidence people are turning up that they're not a secure as they could be would be unnecessary.
  My best guess is they decided to make an email company based in Switzerland with the schtick that they're secure (banks amirite?) They're doing what they can to appear secure without spending too much money. They're not going to have legal battles to keep your data private, and they are going to comply with agencies request for data. Even if they support end-to-end encryption if they are required by an agency to turn that encryption off for you, they're going to do it.
  They're probably less likely than Google or Microsoft to sell all of your data to the highest bidder, but realistically there's no such thing as secure email.

Not likely worth it. Primary reason is that the large federated email services are skeptical of email from services such as your proposed self hosting solution and may simply not deliver the mail you send. This is to mitigate against spammers setting up bespoke servers.
There are a bunch of other things that could go wrong if you don’t set everything up perfectly, but even if you do, this would be a big problem.
Better off using a custom domain with a big provider. Fewer headaches. I like Fastmail, but many others are great too.

Jep. running a linux mailserver for now 20+ years
its now running postfix :-), in a vm on proxmox...
- Proxmox is awesome. Sort of the answer to most of my server wants.

I've been self-hosting e-mail for over 15 years and hope to continue doing so. Although it's being made increasingly difficult by big tech players. I wrote about it here: https://proycon.anaproy.nl/posts/rant-against-centralising-e-mail/
- Aren't you afraid about some important email getting discarded without you knowing about it? Or about unnoticed downtime which results in missed mails?

@DidacticDumbass
Yes I run my own mailserver. I have done it for the last 15 years or so.
I'm also running my own Friendica instance.
- Could you share you solution? You don't have to! I am just curious how you do it since a lot of people seem to hate it, compared to self-hosting everything else.
  
  @DidacticDumbass But yeah you're right. It's a mess nowadays with email hosting because Google for example just rejects everything except the other big services even if you comply with DKIM etc. Fuck them honestly

Yes, and I love it.
I use mailjet as a proxy on outgoing emails so that I get fewer of my sent messages rejected, which works.
It was a pain to setup but it's treating me very well.
- Neato! I was so concerned about the logistics of sending and receiving emails, it never occurred to me that I could get fancy and make nice looking emails. All I use is text, yet I can do so much better.
  
  No, I only write plain text emails, mailjet only has ip addresses that are generally not blocked by the big providers and they do all the DCIM stuff.

I use Cloudflares email routing.
Point my domains name servers to Cloudflares and enable email routing. I can then create any email address in that domain and have it forward to any of my email addresses. Works great when signing up for accounts. The only thing you can't do is fire off email FROM said email address
Edit: can to can't

I used to run my own mail server many, many years ago (early 2000s), but today it's a lot more difficult. I personally don't think it's worth it, but I do have my own domain that I can host anywhere I choose. At the moment, I'm using Fastmail. Lots of nice features, and no complaints.
- Yeah, I think getting my own domain is the first step I have never taken. Closest thing to web development I have done is a Neocities I have not messed with since getting an account.
  
  You definitely don’t need to worry about a web site if you want to just use the domain for email.
  Feel free to hit me up if you have any questions about it. Some providers make it pretty easy I think to setup and manage all of that together, while others require some manual work on your part.

As much as I enjoy self hosting my own services, email just seems like more trouble than it's worth. I let Protonmail take care of that for me.
- Yeah. I am getting great suggestions, but also a lot of hard truths. I think a basic paid email is probably less than I would ever pay to get the setup right.

Only people who hate themselves

I stopped running my own a while ago. Its no longer really decentralized and the big players (google/microsoft) will often just blacklist you for little reason.
That said I DO maintain my own domain and backups. So i can take my email to whatever hosting provider I want.
I also noticed, during the migration, that if you simply register your domain with one of the big players (ie: Google Workspace or M365) you will often get whitelisted and email will flow easier. This was easier when they had a free tier though.
- Got the same issue. Everything was setup properly. SPF, dkim, dmarc was all good. Server IP wasn't in any blocklists. But my messages would still fall in spam with Gmail.
  Ended up setting sendgrid as a relay and all is good now.

Your own email server requires near 100% uptime or you risk not receiving critical emails. If a remote email server is trying to contact your email server and it can't it's only going to retry a few times and then give up. Hosting this yourself sounds great until you realize high uptime is not cheap and requires constant attention.
Setting it up securely can be difficult depending on your understanding of server infrastructure as well as protocols like DNS. You need to set up SPF, DKIM, DMARC, etc in order to prevent someone from faking an email from your server.
Of course, federated email does not use SPF/DKIM/DMARC because the whole point is that someone from another server could use your server to send an email (hence the federation). Open email servers were common 20 years ago but very rare today. That makes setup easier, but the main caveat is that most known non-federated email servers will reject email from servers that don't have SPF/DKIM/DMARC because they generally end up being havens for bots and spam since there is no verification or authenticity of the sender.
As someone who self hosts a lot of things, I would never self host my email. If i did I would be paying for two boxes in different parts of the world on different ISPs to provide that uptime. I would definitely set it up securely and not as a federated server otherwise it would be practically unusable for day to day emails.
- Your own email server requires near 100% uptime or you risk not receiving critical emails.
  I disagree. You can take some amount of downtime without issue.
  https://wpmailsmtp.com/docs/how-to-automatically-resend-a-failed-email/ as an example for some services.
  Many services (including postfix by default) will attempt a number of resend operations before it gives up.
  Of course, federated email does not use SPF/DKIM/DMARC because the whole point is that someone from another server could use your server to send an email (hence the federation).
  What? All email is federated. What are you talking about here? SPF/DKIM/DMARC are on top of email... and have nothing to do with the federated property of email. Federation does not mean that you login or use another server. But that you have your instance, and the servers hash out the cross communication amongst themselves. That's EXACTLY what email servers do using SMTP.
  I would definitely set it up securely and not as a federated server otherwise it would be practically unusable for day to day emails.
  If your email wasn't federated then you would get emails from anyone outside of your own instance. That would make email useless for 99% of the world.
  
  I take "federated email" to refer to a juxtaposition with normal email implementation which harkens back to how it was in the 90s or early 00s where you didn't need to be registered on many SMTP servers in order to use it and it's stripped of server-side validation. There's some discussion on this topic in the fediverse.
  You're right that the default current implementation is already federated.

I don't. But I do have my domain and use a hosted solution, so I'm kind of independent and own my data.
- That sounds like the right middle ground for me. I know for sure my home network is not as secure as it could be, especially since I live with people who need everything online to work without obstacles. I can't even install PiHole.
  But, hosting is probably more affordable in a year than the amount I might spend on coffee in a week. And I typically make my own coffee.

I originally did but the maintenance burden was killing me. Then last year Proton unified their subscription with VPN and Mail (also upgrading my Proton VPN only subscription to Proton plus) and from there I decided to just go all in on Proton mail. I integrated my domain to Proton mail and never looked back.
- Same. One day I realized that emails where toi important for beeing host by an amateur me. 😉

I did for a couple years, but moved to mailbox.org a while ago. The effort was much to high to save a few bucks and there is no real upside to it. E-Mail is a troublesome mixture of different protocols from the internet stone age held together by chewing gum (SMTP, POP3, IMAP, DNS, database or file storage, maybe ActiveSync, Web-Mailer, ...)
Even when everything is up and running there is always maintenance to keep your SSL certificates up to date, update your incoming spam filter technique, keep other mail providers assured that you are not spamming (DKIM, etc.), keep all the different system services (see above) up to date and interoperable, etc. and every few years when you want to move to a new server, provider or Linux distro you start it all over again.
- Damn, it is so bizarre that email of all things would be the least operable by tech savvy individuals. Someone linked an article that explains it, and it truly is depressing. Like, it makes me not want to even have email... which is not really possible if I want to be employed. Eh, it's not like I DON'T already have free email accounts, I just don't always like the decision my provider makes.
  
  Well, there are plenty of providers out there there should be one that suits you. Having a domain of your own with DNS access and letting the provider doing the hosting is not (so) hard and gives you the flexibility to switch any time.

E-mail was the first "thing" that got me off of Google (to Proton & then currently Tutanota) but is really the last remaining service I not have self hosted.
I have always read about how difficult and time consuimg it was to run your own mail server, but I felt like I needed to experience it myself. So I purchased another domain and followed the instructions on https://mailinabox.email/.
I am using a small VPS on Hetzner and I have to say the experience has been almost flawless so far. I did need to have my new domain taken off the Domain Block List, but Hetzner gave me a clean IP and defaults to blocking port 25 outbound to prevent spam (simple ticket to open, once account is 30 days old and paid).
I know I'm still early into this journey so far, but it has been really simple and I plan to test this secondary domain for a few months before moving onto it full time.
As an avid self hosted of literally everything else, I can say it has been a lot of fun learning so far!
- Hell yes, I love the enthusiasm! I just got a domain, which is giving me 3 months of email, so that is great. I feel like Tutanota is the most honest email service when it comes to advertising privacy, and they do some stuff that Proton definitely does not, like make recovery impossible without a key, and use no other method.
  My next step is to get a VPS, and Hetzner is the name I have seen pop up the most. I will use that.
  Thank you!
  
  Yes I haven't had any real issues with Tutanota, but it seems like the common trend is that they, and everyone else, is raising prices for things I dont really need. But at the same time, the things I do need, I.e. accounts with enough storage for my family, will start costing more than the price of renting a VPS alone. So for me, its partially privacy, but also ownership of my data and cost benefit analysis where I am now trying to make CERTAIN that my self hosted email is worth the cost savings.