We have been on iRedMail for a little over a year now. The server is running on a CentOS7 VM in a VMWare environment. We have 343 users across 3 domains. The performance is fantastic.

Support is also fantastic. I've only had to open one support ticket and within 20 minutes Zhang responded to the request. I can't imagine how long I would've had to wait for one of those high priced solutions.

If you have more than 25 users I recommend paying for the license for iRedAmin-Pro. The interface is very intuitive and makes email administration very easy. Setting up blacklists/whitelists, managing greylisting is a breeze. User setup and management is very easy with the Pro version. Also, when a young bride wants her email address changed it is so easy compared to what I had to do on our old mail server.

If you are looking for a DIY solution, I strongly suggest going with iRedMail.

Kevin
Buffalo, NY