Just fired up an old copy of Win10 again, and after update that environment is showing problems connecting to Exchange 2003. Specifically, Edge is unable to connect to Exchange Web Mail, and Outlook 2003 is unable to connect to Exchange (using the exchange protocol).
I've got no firewall and no virtualization. I suspect an authentication or encryption error. SMB1 is enabled. IE11 still connects to Exchange Web Mail, so it's not a simple certificate error, nor even a simple network error: Exchange is refusing the connection for some other reason. It wasn't a problem a couple of years ago when the Win10 machine was last fired up. And I can still connect from Win2K: it's not a simple Outlook connection error.
As far as the real world is concerned, Exchange 2003 is definitely retro-computing. It is a server system (most of retro-computing deals with client systems or workstations), but I'm hoping you won't cancel me for that.
Generally, what can cause connection failures when trying to connect from new systems to old systems? Specifically, what can cause connection failures when trying to connect From Edge/Win10 to Exchange 2003/Server 2003?