To open a received file, save the attachment on your disk, and then double-click it.
If it’s an NWF file, Autodesk Navisworks searches for the referenced files first using the absolute path that the sender originally saved the file with. This is useful if a team is on a local network and the files can be found using the Universal Naming Convention (UNC).
If Autodesk Navisworks is unable to find the referenced files, then you need to save the attached NWF file in a directory where all referenced files are located. Autodesk Navisworks can then search for the files relative to the master NWF location.