Similarly, faced with the same problem
as razor put Postfix in front of Excel, spam became less significantly less
I used to cut off the attachments ( everyone always name was *zakaz*) but then the pests have become smarter, and the text is sent the download link
Our Buhi gullible, though warned several times not to climb where do not ask.
The specifics of obligation to keep open all sorts of hugedrive, mail disks, dropbox and so on.
I helped the Postfix previously fought with Excel settings, are now fighting with Postfix :)