The issue is the request is not being processed by Sitecore, since it is seeing
.oldRegistration as file extension and it has not been configured as an allowed extension. You need to add all the extensions that you want processed, since the module works integrates in the Sitecore pipelines:
<processor type="Sitecore.Pipelines.PreprocessRequest.FilterUrlExtensions, Sitecore.Kernel">
<param desc="Allowed extensions (comma separated)">aspx, ashx, asmx, oldRegisteration</param>
Note that the above is in the
preprocessRequest so is very early in the pipeline process. Also be aware that configuring and allowing too many extensions will cause Sitecore to process them and may have a negative impact on performance. It's worth considering the use of the IIS URL Rewrite module for "static redirects", i.e. one's that do not need to be configured by users, since it works at an IIS level before any request to your application is made.