How to build a secure mail server?

Question

postfix

Good afternoon colleagues!
The task was set to build a secure corporate mail server! my eyes fell on Zimbra Collaboration because it has a very user-friendly interface and a lot of goodies!
Interested in the question, is it worth rolling Zimbra or is it limited to installing iRedMail with a roundcube web muzzle?
Also interested in the principles of building a server protection system against attacks and server hacking, how to build a protection system? is it worth enabling SELINUX on Centos 7? or you can configure everything completely on standard access rights!
Looking forward to your advice and thanks in advance for taking the time to read!

Answer 1

How to build a secure mail server?

First, decide what you want to protect against.

Answer 2

Dmitry already answered you, but to orient you on my own I will add. We protect against:
- external and possibly internal brute force
- spam from outside
- possible spammers within the company
- our anti-spam system is profiled and each user has a friendly interface (he can save his mail that got into spam - false positive, he can train the antispam system)
those who wish can continue the list, but this is the main thing. And it doesn’t play a strong role what you take there, the main thing is that you understood how it works.
For example, I am not a supporter of "ready-made assemblies", I think that they discourage the desire to understand. You can use them when you already understand everything, and you are too lazy to do it with your hands.
I consider it a normal practice for a beginner to install and configure the software separately and in the console. This is IMHO