Webmail on Plesk server is not available: 404 Not Found/403 permission denied

Symptoms

• Unable to open the Webmail going to Domains > example.com > Email Addresses > Webmail, it might show one of the following error messages:

  CONFIG_TEXT: Not Found
  The requested URL /roundcube/index.php was not found on this server.
  Apache Server at webmail.example.com Port 80

  CONFIG_TEXT: 404 - File or directory not found.
  The resource you are looking for might have been removed, had its name changed, or is temporarily unavailable.

  CONFIG_TEXT: HTTP 404. The resource you are looking for (or one of its
  dependencies) could have been removed, had its name changed, or is
  temporarily unavailable. Please review the following URL and make sure
  that it is spelled correctly.
  Requested URL: /default.aspx

• When opening webmail.example.com in a browser, Plesk default page is shown.

• DNS webmail.example.com resolves to an IP address 203.0.113.2:

  # dig +short webmail.example.com
  203.0.113.2

• The IP address of the server where webmail.example.com is hosted is 203.0.113.3.

• Domain example.com was migrated from another server.

Cause

Invalid DNS record for webmail. The domain name webmail.example.com resolves to an incorrect IP address.

Resolution