How can I block emails with no sender?

I'm RoadRunner also. This worked for me:

Set up a rule "From", "does not contain", "@".

Set up a rule "From", "does not contain", "@".

I suspect you'll get junk with any email system. The key is how you manage it. With filters and rules, you can keep it to a minimum.

Who is your email provider? Is it Apple Mail or something else?

In that case, and admittedly I'm a cut-to-the-chase kind of user, I'd shutdown, restart using Command + R to get to the recovery panel and reinstall the OS.

But that's just me; I'm fully prepared with multiple backups and a backup Mac to cover me in case the plan goes awry.

I've setup a key combination, Option+Delete, that moves the email to the trash and empties the trash. I haven't deleted an email the regular way in over a year so didn't remember how many operations it took. It was just some food for thought.

I was on the phone with Apple support for another matter and brought this up. I was told there's nothing that can be done about it and to just delete them as they come. As good as Apple support has been for me, this left me wondering, what the heck?

The only remedy I came up with was to go to my internet provider (Spectrum) and dive into my email settings there, marking one spammer with no email return address as "junk mail" and they automatically moved all of them to the junk mail folder. When I returned to my Mac's email page, they were all in the junk mail folder as well. I hope this solves the problem.

Haven't tried this with Apple Mail.

Some Windows users were having the same problem with "No sender" spam, and someone came up with the idea to set their mail filtering to move ALL e-mail into (a junk folder, or the trash), EXCEPT for e-mails where the sender field contained a '@'. The idea being that all legitimate e-mails (as well as many others) would have the '@'.

https://answers.microsoft.com/en-us/outlook_com/forum/all/how-can-i-block-spam-email-with-no-sender-email/1ad8e13e-8dc9-4d7f-9b7c-24217094ec3b?page=1

I have the same (or similar) problem, but there is just one piece of text in every one of these junk emails - a 'Remove-Me' at the bottom with a link that I'd never click on. I set up a rule to delete anything with 'Remove-Me' and that works.

I agree. A smarmy arrogant response not worthy of Apple - I hope the attitude isn't endorsed by the corporation. I too have just recently started seeing these types of emails; there is no way to block them as junk; it's clearly a new weapon in spam wars, and one way or another Apple is going to have to deal with it. So, let's get cracking.