[mecer]

Am I missing something? Why not just create a filter that permanently deletes or marks emails from a certain sender as spam?

[simmons]

That doesn't catch the cases where the sender uses a different From: address, or shares your email address with third parties.

[mecer]

Ah, I see. Looks promising then!

[kazinator]

Because that is a spam-fighting approach that, by itself, last worked well in 1993.