The mail clients, such as thunderbird or evolution are well equipped to deal with spam. You mark mails as spam and they learn to move it to the junk folder over time. Or you can add filters if the pattern is easy enough to figure out and the spammer is aggressive.
When receiving documents and messages via SecureDrop or Nextcloud, the problem is essentially the same but there is no tooling to deal with people who are very persistent (for instance sending documents about aliens taking over the government on a daily basis).
Any ideas on how people deal with this problem? Clever methods that do not involve developing new tools? Or, ultimately, new tools that should be developed because nothing else works?