GNR has a specific Output directory structure. If GnR is sending emails stripped of their attachments and the people are sure that their firewalls and such are not removing them, then you need to check to make sure that this structure is present in their installation.

In OPSSQL root folder (usually c:/opssql) you need to create GNRoutput folder
Inside GNRoutput folder just created, you need to create 3 more folders Graphs, Reports, and Temp.

These are used by the GNR PDF printer to create the file before attaching it to an email. Make sure these exist.