Other people can upload files to a project without being invited, by using the Inbox. This enables people to upload files through the inbox of the project by simply sending an email.
From there, documents can be moved to the correct location in the project by a Project Admin.

1. Open the Settings tab.
2. Click the gear icon in the Inbox card.
3. Tick the checkbox for Active, registered users and approved senders below,
4. Type the email address of a person not invited to the project, and press Enter.
5. Click Copy Inbox Address to share with them.
6. Click Save.

Note: When someone sends an email with an attachment to your project, only the attachment is uploaded to the Inbox. The subject and any text in the email are discarded.