ISPConfig 3 Roundcube Plugin on Debian 9 (Stretch)
Setting up Roundcube webmail – workaround.org
Roundcube/Horde webmail and websites on FastCGI are not accessible: Connection reset by peer: mod_fcgid: error reading data from FastCGI server – Plesk Help Center
Using RoundCube Webmail With ISPConfig 3 On Debian Wheezy (Apache2)
How To Install Latest Roundcube Webmail On Ubuntu 18.04 LTS | HostAdvice