What has completely decimated mail management in my experience had been the rise of cryptolocker related emails. You could always deal with traditional viruses

What has completely decimated mail management in my experience had been the rise of cryptolocker related emails. You could always deal with traditional viruses by blocking certain types of attachments. A false negative on spam just annoyed someone with some Viagra sale they probably didn't want. Nowadays, you fail to block an email and suddenly a user loses his entire department's file share for the day.