John,
One thing you can quickly check is that you can access the BOSH URL from your browser. There's a slim chance that there is a certificate problem of somesort. You should see a page describing the XMPP protocols supported when you navigate to the BOSH URL.
More likely there is some difference in Office 365's IE 11 (though I could not find such differences documented anywhere). IE 8, 9 and 10 used an XMLDomainRequest object for cross site scripting. This object came with restrictions that did not allow CORS with different protocols (an application can not be served as http and access a cross site script to an https URL). IE 11 removed the XMLDomainRequest object and replaced it with CORS for XMLHttpRequest (XMLHttpRequest enhancements (Windows))), something jQuery supports directly and which does allow differing protocols.
The problematic piece of code you identified above would only execute when CAXL was trying to (essentially) proxy an XMLHttpRequest using an XMLDomainRequest. If the XMLDomainRequest object was undefined (IE 11) that particular piece of code should never execute. So it must be that IE 11 in Office 365 implements XMLDomainRequest and therefore has the same restrictions as IE 8, 9, 10.
CAXL 2014.04 added an additional check to always use jQuery's CORS implementation if supported. That check must be failing as well, meaning the only way CORS will work at all in Office 365 would be to keep using XMLDomainRequest. In other words, CAXL cannot be updated to handle the problem you are seeing.
A possible work around would be to make sure you are serving your app from the same protocol as the CUPS server you are trying to connect to. I found this discussion that may be applicable: Issues with performing an ajax call within an Office365 app for Excel
I could be wrong about all this John. I didn't spend a lot of time looking for blogs or similar problem reports posted on the web. But I did some debugging to day to make sure CAXL was using jQuery's default XMLHttpRequest implementation on IE11 in Windows 7 and 8.1, and that CORS was working correctly when using different protocols. In all cases jQuery reported that the browser supported CORS and that the XMLDomainRequest object did not exist, and CAXL worked appropriately.
I wish I had better news, John. Perhaps the blog posting will provide a work around.
Joe Fuhrman
CAXL Developer
<jofuhrma@cisco.com>
