The Metalogix SharePoint Extensions Web Service enables a number of features that would otherwise not be technically possible to provide. It is a free web service component that comes bundled with Migration Manager for SharePoint - Website Edition.
The Metalogix SharePoint Extensions service was built to overcome some limitations of the SharePoint web services. The Extensions Web Service allows us to use the SharePoint API to write data to the target that would otherwise not be possible to do remotely. Additionally, the web service also improves write speeds of Migration Manager for SharePoint - Website Edition dramatically.