Server: Win2003 sbs, Exchange 2003Client: WinXP Outlook 2000.I can get my POP3 mail from outside the office, and I can get my email on the server itself, but whenever I try to connect to check mail from the XP machine with Outlook or with Thunderbird I get "Connection refused". This started happening after a MS patch of Exchange a month or so ago.The problem is that I don't know if its being blocked at my router or if exchange got some idea that accepting internal connections is a bad idea.I swear to God: Microsoft is gonna make me insane.

What patch did you install? If you didn't make any changes to your router I would doubt that's the issue.