Having search for a solution to replace an Exchange + AD system with an OpenSource solution for a while. Did look at Kerio, Zentyal, Kolab, Kopano, Zimbra and Sogo from their respective free/open version, and also made a deep investigation into the available documentations and forum contents.

So far the iRedmail packaging is the far best I've seen, and answers to almost every questions I come across can be found in the existing iRedMail documentation or on the forum site.

Since all modules are "standard" open source projects, it's easy to find more information for specific issues, like OpenLdap or Postfix elsewhere.

Once I tried the installation and got it up and running in an hour or so, I didn't bother to check the other test systems again. We have now started a project to migrate our Exchange server, and to use OpenLDAP instead of Active directory for our application servers (Gitlab, Confluence, Jira, etc).

Thanks for a really good product.