You may experience "Page Not Found" errors when trying to access your webmail (Horde or Squirrelmail) from behind a corporate or highly restrictive firewall. There are 2 ports that must be open on your firewall depending upon which method utilize for accessing webmail.
If you are trying to access webmail via the unsecure method (http), the following ports on your firewall must be opened to allow TCP traffic:
2092
2095
If you are trying to access webmail via the secure method (https), the following ports on your firewall must be opened to allow TCP traffic:
2093
2096
Normally, most networks do not block these ports, but if they are blocked, access will be prevented.
