Does anyone know anything about setting up a proxy to use with an arbitrary (or specific) IM protocol/client?

This is specifically so a friend can get around their corporate firewall which is apparently blocking specific ports on specific servers. No IM service seems tobe working for them right now.

I'd like to install a proxy on either my hosted or local servers for him to use to connect to the IM servers on alternate ports. Adium (using libgaim) for Mac OS supports a proxy configuration per account, so the only piece missing is the actual proxy installation/setup. Mac OS X (local server) or Linux install (hosted server).

The proxy connection itself doesn't need to be encrypted as Adium has its own encryption which will hopefully continue to work through it.

EDIT: I remembered that OTR (the encryption lib Adium uses) is also available in proxy form. Should this be enough to do what we need:

http://chris.milbert.com/AIM_Encryption/ (the proxy section is below the default Adium setup stuff at the top)