This is extremely cool, I just had to blog about it! Many company firewalls are very strict, blocking as many ports as possible. And because cPanel, WHM and cPanel webmail are on ports other than port 80 (ports 2082 and 2086 respectively), they will quite often be inaccessible. Well not anymore!
There's a cool open source PHP script called cPanel Proxy, which enables you to have almost full access to cPanel, WHM, and webmail from behind a firewall, on port 80. You just need to place the script in subdomains on your domain, and you can customize the subdomain if you wish. I say 'almost full access' because I have run into two errors:
1. After sending emails, I get 'page could not be displayed', even though the email sent successfully.
2. I can't edit .htaccess files in the cPanel file manager.
Oh well, it's still great!