Disclaimer: I run a fairly large mail system at work, and have been for more than 15 years.

The issue isn't setting up a imap/smtp daemon, that's easy, the hard part is authentication, performance, and filtering spam:

Authentication:
If you use some backend database like mysql or ldap, then it's fairly easy to make the username the email address, which is expected on most mail clients, but if you want to use your standard username because you don't want email to have yet another user database, then you either need to force the mail clients to use just the username, or you need tell the mail system how to map the username to a mailbox/email address. Speaking of that, you can have multiple email addresses per mailbox, but if you are using the email as the login, then which one?

At my job, our mail system will allow you to you authenticate as your username or any of the email addresses that the user gets mail for. It required a bit of mapping which I don't think some of the simpler imap servers can do.

Don't forget about account lockouts and such as any public email server is under constant attack.

Performance:

Mbox format is terrible as you must open a huge file (some users have a terrabite of mail) so I don't recommend it, then there is maildir, which is one message per file, which is better, but when you attach a new client to it, it must open/parse/close hundreds of thousands of files. Cyrus gets around this by using maildir and adding some of it's own indexes. Dovecot does some of this too from what I understand.

Keep in mind that the indexes must be sync'd up, which can get complex if you have to restore from backup.

Filtering spam:

You must use DKIM if you want to send email to gmail these days, so you have to have that sorted out, and it needs to be the last thing you do before you send the message. This requires there to be some interaction between the spam filteirng system and the MTA. Depending on how you set all of this up, there can be back scatter issues, or performance issues. I like mimedefang for this as it uses the milter interface which is really nice as you can drop email DURING the smtp transaction. Setup isn't trivial though, and it takes time to setup all of your rules.

I could go on for weeks about spam filtering as you can't trust any one spam filtering system, you need to implement all of it before it starts to get anywhere near effective, but I will say this: You really must know what you are doing and be proactive in maintaining it.

So, if you just want to play around with it, sure, anyone can do it, if you want it to actually be useful, it will take a bit of work, unless you are cool with getting lots of spam, being rejected as spam, and only have 100 users.

schu

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I had a big mail structure with slackware, qmail and dovecot in the past, it took a lot of work for everything run flawless, but worked really nice.
It was 3 servers

1.Slackware Mail router and Filter (Heavy modified Qmail with DSPAM and ClamAV)
2.Slackware Mail server (Qmail with vpopmail and dovecot)
3.Slackware webserver with Horde groupware.

Today i am using postfix with centOS.

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I came across this some time ago when I was looking at setting up a mail server. Maybe you can glean some tips from it since it is a little old:

https://gerardozamudio.mx/2015/04/25...x-and-dovecot/

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Hey, thanks for linking that I actually updated the article for 14.2 back in January 2019 so it should be pretty up to date as far as 14.2 goes. Postfix has been included in -current along with a couple of other things so I'm working on a separate article for -current to have it ready when 15.0 ships.

Feel free to ask any questions in this thread if you need help. I've been running that setup for about 5 years now with no issues whatsoever.

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I didn't even see that you updated it. I must have been looking at it before you did, I just had it bookmarked (now updated).

My server is not running a mail server as I was looking at, that's too involved for me right now and I don't trust my hardware enough to serve it for any long period of time. I have a better/newer MoBo for it, but putting it off until I get a better CPU for it.

It is currently running Gitlab (12.3.5) with a bundled nginx, which I need to figure out how to use that nginx to serve other things like Wordpress or MediaWiki, or install a newer nginx (1.16.1) than SBo has and serve Gitlab through that. Also putting that off, just because I'm lazy.

I'm watching this thread closely and taking notes. My friends-and-family server has been providing email service for 22 years, and it has morphed over the years into a frankensteinian mish-mash of qmail, qpsmtpd, stunnel, inetd, imapd, popa3d, and the only one of those whose sources I haven't kludged extra features into is stunnel. The spamfilter is 2620 lines of original perl which integrates a few other spam filtering systems and over a thousand regex rules into a unified karma system.

It's a nightmare which I cannot recommend to anyone, and it really needs to die and be replaced with a cleaner system at some point, but I keep putting it off because it works and I don't want to introduce any new glitches to my users (one of whom is my wife, who is VERY reactive to email glitches).

So please, keep telling me about your systems. Everything you write, I am reading voraciously.

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