After upgrading to Messaging Gateway 10.7, you find that PDF attachements are triggering an Executable Files content filtering rule. If you are using the default Delete Executable Files Violations content rule, this will cause some PDF attachments to be deleted.
The malware scanning engine was improved in Messaging Gateway 10.7 and later releases, which resulted in a change in how files are scanned and embedded items are detected.
To change this behavior, remove the .js extension from the attachment list used by the content filtering rule that has taken action on the message.
If you are using the default Delete Executable Files Violations content rule and the default Executable Files (default) attachment list, you can address the issue as follows:
Extension checking is not generally reliable and True Type file checking is the recommended way to determine a file's actual type.