What appears to have worked for this specific issue is to enable DomainKeys in cPanel which is accessed through Email Authentication.
I say "appears" to work because since I did that, I haven't had any spam with a blank From field. Perhaps that "spam method of the month" just came to an end, but that would be quite a coincidence.
I suppose I could disable DomainKeys to check, but why mess with a good thing? I still get spam to that address, but none with the blank From field. For that matter, it may also be trashing other spam, but I wouldn't be aware of it.