You can add documents to a Vault via email. Files are saved directly into a folder on any Vault, as long as your file is sent as an email attachment. The folder will be created in the root of the Vault.
You want to mail to a subfolder, follow these steps.
The unique recipient email address can be found on myNomadesk.com under the Vault properties.
Note:
You can also let people that don't have access to your Vault use Email2Folder by checking the Anyone can email files to this Vault option under Users & Permissions in your Vault.