Outlook 2016 error 0xCAA70004

Alex MelchingThanks for linking that article; it gave me the clue I needed to solve this problem.

Configuring Windows 10 to access the Internet through a local proxy server (such as Privoxy) creates issues for Universal Windows Platform apps, which by default are forbidden from opening a network connection to the local machine. This includes the Azure Active Directory (AAD) broker plugin used by Office applications to perform authentication, which is effectively blocked from accessing the Internet when a local proxy is in use.

The solution in this scenario is to use a tool like Tiago Andrade e Silva's Loopback Exemption Manager to explicitly grant permission for this plugin to access the local machine, thereby allowing it to connect to the proxy server and, through it, the Internet. Once I added an exemption for the AAD-broker plugins on my computer I was able to sign into my Office account again and use Outlook without the "0xCAA70007" error code reappearing.