When you receive a document from an unknown email, you can block this email from Unfiled section.
Sign in to your account and go to Documents> Unfiled.
Click the name of the document with the red message "Unrecognized email address" to activate the preview of the document.
Click the "Block" button.
The system will show you an alert letting you know that no more emails will be received from that address. Click "OK".
A confirmation message will show. Click "OK".
You can always manage your blocked email list in My Account Settings> Security. There you can remove or manually add the email address.
• To manually add an email address click in the plus button next to the title "Blocked Emails".
• Manually add the email you want to block.
• Click the "Save" icon.
• To remove it, just click in the "X" next to the email address.