For anyone who has had the annoyance of trying to backup a Cisco Unity Communications based server to a Windows based server, you will know how annoying it can be.
I recommend Syncplify.me Server! and it has a how to for its older version of Server!. They have obviously changes it to a web based program in newer versions.

The new version is similar in that there is a one click setting in General Security Settings

This basically sets the server to use the SSH File Transfer Protocol Version 3

Everything else from the article applies such as the username and folder structure, so ensure you read the rest of the article from “Now that you have properly configured Syncplify.me Server! as a backup target for Cisco UCM, you have to properly configure your UCM side too”

Edit: Link broken on Syncplify link, changed from