I finally got a reply from my false positive submissions. No explanation was given, however, as to what the actual issue is. I still think the redirects that the autodiscover.xml file uses to find the closest Microsoft server(s) is falsely being detected as malware. At least it's fixed and my users aren't being blasted with Avast warnings.
An email they sent reads:
Hello,
Thank you for contacting Avast.
Our virus specialists have been working on this problem and it has now been resolved. The provided website isn't detected by Avast anymore.
We are sorry for the inconvenience. If you have any further questions, don't hesitate to contact me again.
Best Regards,
(name hidden)
The Avast Support Team