This is a global header-from blacklist for use with rspamd.
I have collected a large number of spammer domains, these are primarily investment, crypto and stock related newsletters that, while they often have unsubscribe links, were never granted permission to email in the first place - they're obviously sharing and/or selling/reselling the same email addresses over and over again.
New ones seem to pop up pretty frequently, but this has dramatically cut down on the trash that hits my inbox.