Lately, I’ve been getting emails with no subject, no “from” and no content. Nothing but a return path, which I wouldn’t see if I didn’t display full headers. It’s just an empty email. I just got about half a dozen of them at once, each from a different return path.
Any theories about this?
The Matrix has you.
I’d guess someone’s buggy spam/email worm program. Or maybe someone upstream is stripping out a trojan payload from the emails. Does there seem to be any pattern to the hosts that are originating the emails?
No, they’re from all over (e.g., Japan).
Could be from a botnet. Also, any path headers except the last, added by your ISP reporting who sent it the email, can be forged.
Possibly somebody testing a spam program. Or, maybe there is a hidden link, if this is still possible, where the text is the same color as the background. Try moving your cursor around the content and see if it finds a link – but don’t click on it, of course.
You can “view source” of email messages in most clients, which will show the plain text content of rich-text messages. That would be simpler, I think, than waving the cursor around on a blank screen.
Most likely doing a verify of an email list. They’re looking for bounces while giving the junk filters little to work with. I personally have my filters set so if there’s not subject, it’s junked.
Alternatively it’s a test of various open relays.
Now that you are the target of the activist left, it is a good idea to make sure there are no vulnerabilities in your security.