Unable to open the Webmail of a domain in Plesk: 500: ERR_CONNECTION_TIMED_OUT

Symptoms

• An attempt to access a domain Webmail in Plesk fails with:

  500: ERR_CONNECTION_TIMED_OUT

• The following messages are found in the Apache error log ( /var/log/httpd/error_log or /var/log/apache2/error.log ):

  AH00112: Warning: DocumentRoot [/usr/share/roundcubemail/public_html/] does not exist
  AH00112: Warning: DocumentRoot [/usr/share/roundcubemail/public_html/] does not exist
  AH00112: Warning: DocumentRoot [/usr/share/roundcubemail/public_html/] does not exist

• Plesk Premium Email extension is installed.

• Web ports 80 and 443 are not filtered by any Firewall.

Cause

Not all packages needed for Plesk Premium Email extension to work were installed.

Resolution

1. Login to Plesk

2. Go to Extensions > Plesk Premium Email > Open

3. Press the "Install" button near the message "Plesk Premium Email: Necessary packages are not installed"