Typically it's unnecessary to adjust the default SSRS email report settings, but sometimes it's unavoidable. For instance, in our case we needed to expose the SSRS web portal on a specific URL.
We're using the latest version of SSRS: SQL Server SSRS 2016
I found several references and guides on how to change this via the SSRS configuration file:
All the guides correctly identified the <UrlRoot> node. However, what was not made clear was what value to use.
After some trial and error the solution was:
Restarting the SSRS services is required after making this update.