In this guide, I will show you how to make a Linux Mail Server in fast and easy way. This guide was taken from tiq's tech-blog for recent version, Linux distro I using is Ubuntu 20.04 LTS
Make sure you have Certificate and Key file ready to use.
You can use existing Web Server SSL certificate, since we going to use same domain, example.com.
If you plan to use mx.example.com or mail.example.com you need create another one for these.