Ah, now I had a link to something like that.... and here it is. This is a list of all the Well Known (0 to 1023), Registered (1024 through 49151), and Dynamic/Private ports (49152 through 65535) as of 2008-09-26. It's a bit confusing when you first scan through it, but have a read an I'm sure you will get the gist of it. Also, the page is VERY long, so give it some time to download entirely, or better yet, save it to your local hard drive.
http://www.iana.org/assignments/port-numbersThese are the basic ports that need to be considered. With these ports open, your clients will be able to browse the internet and check their email. The cornerstones of the internet. Anything over and above these ports is ultimately up to your discretion.
- TCP/UDP 67 - DNS (only needed if your clients point to an external DNS server)
- TCP 80 - HTTP (only needed if port 80 is not being intercepted by the WWW Proxy server)
- TCP 443 - HTTPS
- TCP 25 - SMTP
- TCP 110 - POP3
- TCP 143 - IMAP4