I used to proxy my instant messaging (IM) throw Squid in Fedora 3 and it worked fine. What I did was to enable CONNECT in any port, not only to the listed SSL ports. So, I commented the following line in /etc/squid/squid.conf: # Deny CONNECT to other than SSL ports #http_access deny CONNECT !SSL_ports Now I know a better approach is to list the ports I use in my IM client (Gaim) in the list of allowed SSL ports and let Squid deny other ports. i.e. include ports 1863 (MSN), 5190 (AIM/ICQ) and 5222 (Jabber) in SSL_ports: acl SSL_ports port 443 563 1863 5190 5222 # Deny CONNECT to other than SSL ports http_access deny CONNECT !SSL_ports Now that I've upgraded to Fedora 4 (in fact I did a fresh install), I can no longer proxy IM throw Squid, now I'm receiving 503 (service unavailable) errors: /var/log/squid/access.log: 1120832745.447 5004 127.0.0.1 TCP_MISS/503 0 CONNECT jabber.org:5222 - DIRECT/- - 1120832748.639 256 127.0.0.1 TCP_MISS/503 0 CONNECT login.oscar.aol.com:5190 - DIRECT/- - 1120832762.732 527 127.0.0.1 TCP_MISS/503 0 CONNECT messenger.hotmail.com:1863 - DIRECT/- - I'm running Gaim (IM client) in the proxy host for testing purposes. If I disable proxy in Gaim it connects, indicating there is no problem with the connection itself. but when I switch it to use proxy, I receive the errors above. Any ideas?