Don't bother running a mail server. It's hell. I did from 1998 until about last week. I started running it on a cable modem with an old Compaq desktop, migrated to a dedicated server (which hosted a load of other stuff) and finally onto VMs.
I have spent hours getting myself of blacklists after entire IP ranges were reported. I've spent hours working out why the hell Postfix won't talk to dovecot on a local socket, upgrading Linux distributions, postfix and dovecot and being fucked over by config format changes and periodically losing entire mailboxes to IMAP bugs. Oh and SELinux - hours of it.
The thing that finally killed it for me was Yahoo. My landlord uses Yahoo mail for comms and Yahoo just decided to stop accepting delivery from my server. It took a phone call from me asking him why he hadn't sorted something for me and for him to tell me that he didn't get the email to discover this. So I dredged through the logs, found an error from yahoo's mail servers saying I need to hit a web form to prove I was a legitimate sender. So I did that, and nothing, not a sausage happened. Googling around says I need to wait 6 months before submitting the request again.
I have no power in this situation. I can't email my landlord. I need to do business, not piss around with politics.
So in a fit of anger, I blasted my VM on Linode, went to my local supermarket, bought a Moto G2 in cash to replace my Lumia 630 (which was doing IMAP) that I just smashed the screen on, signed up for Google Apps free trial and just moved the domain over to that.
Just can't be fucked with it any more. I run "inbox zero" (i.e. I delete religiously) so there is no cost for me to migrate.
I don't care if they read my email or shop me to the feds; I'm tired of herding servers and software these days. A decade ago I could quite happily spend all day doing it but I have better things to do now.