As a start of D8 port, we should create a new D8 branch of Mailhandler. Info, module files, configuration, schema, install hooks. Create a minimal proof of concept. This will include creating new plugins for Inmail - a body-email handler that will be able to create a new node by filling the body field of a node from email body. This could require work on Inmail issues in order to get it into the state where it can be used well to integrate with Mailhandler.