Just a suggestion for the installation guides, since my last server I built was back in 2014 and I just rebuilt it 5 years later, I came across something that might need to be added. After getting everything installed and working, I went back and added the ISPConfig3 plugins for Roundcube like I had before. However, the iscpconfig3_account module wouldnt connect. I dug back into the forums and found the answer which was to update Pear and/or Pecl. So I ran the "pear upgrade" and it worked fine but pecl didnt find anything to upgrade. After upgrading Pear, the module start working just fine. So maybe at the end of the guide or somewhere in an appropriate place, upgrading Pear could be added so that it helps avoid the Soap Connectivity issue. Again, just a suggestion since unless you're building ISPConfig3 servers frequently, this would be something that could easily be forgotten.