Horde/Roundcube webmail is unreachable with one of the following error messages in a web-browser:
The requested URL /roundcube/index.php was not found on this server.
Apache Server at webmail.example.com Port 80
The requested URL /login.php was not found on this server.
The requested document was not found on this server.
Web Server at example.com
When opening webmail.example.com in a web-browser, the Web Server's Default Page is shown or the page it is redirected to the domain example.com.
Webmail configuration is missing in Apache:
on CentOS/RHEL-based distributions:
# httpd -S | grep "webmail.example.com"
on Debian/Ubuntu-based distributions:
# apache2ctl -S | grep "webmail.example.com"
Misconfiguration of the web-server.
Connect to the Plesk server via SSH.
Make sure webmail configuration is included in Apache configuration file
zz010_psa_httpd.confusing the command below:
on CentOS/RHEL-based distributions
# grep webmails /etc/httpd/conf.d/zz010_psa_httpd.conf
on Debian/Ubuntu-based distributions
# grep webmails /etc/apache2/conf-enabled/zz010_psa_httpd.conf
If the line above does not exist, add it using a text editor (for example, the vi editor).
Repair server-wide configuration:
# plesk repair web -server