Why does this appear in the server properties?
DeltaSync uses HTTP (the same protocol as the World Wide Web uses) to send and receive messages and contact and calendar data. Other mail services use protocols like POP3, IMAP and SMTP to send and receive messages. Those protocols need to know which mail server they are supposed to be connecting to, usually entered in the form mail.domain.tld.
DeltaSync knows which URL it has to connect to via HTTP; the URL is only given for your information. You'll probably find that you could change it on the properties sheet to http:// mail.mickey.mouse without this making the slightest difference to your being able to send and receive email.
Has Microsoft/Windows Live changed this or is it malware?
I think it was in 2008 that DeltaSync_v1.0.0 was upgraded to DeltaSync_v2.0.0.