I used to have some Win XP Home & Pro PCs using Outlook Express which, although not supported, I managed to get to talk to an Exchange 2003 SBS Server by creating POP email accounts specifying the Exchange Server's IP address in both the Incoming & Outgoing Mail Server boxes, the user's Active Directory logon name in the 'Account' box and their AD password in the password box. It worked!
Unfortunately those pcs are now long gone so I can't refer to them but I need to do this fudge again, albeit using Outlook 2003 rather then OE. Snag is I can't get it to work: Clicking the Test Account Settings button produces errors on the incoming tests as per my screenshot, although the outgoing side gives green ticks ok. Funny thing is that I get the automated Microsoft test message coming in.
Maybe the passage of time has dimmed my memory as to the precise config required, or maybe it will only work with OE rather than Outlook, though I'd doubt that.
Using default port numbers : Don't see any reason these should be changed.