The second would be an opt in Email moderation service. Similarly to only receiving email from confirmed or extended confirmed accounts, this would enable editors to opt all or parts of their email via the "email this user" function into a moderated stream. Much as with moderated posts to lists like this, a list admin would see the email and either approve it or take other action. You'd presumably need to having something on the send email screen to say that "this editor has opted into email moderation and your email will be delayed slightly before being screened and forwarded" You'd also need a group of volunteers to do the moderation, spot abusive emails and block abusers.

The third would be an AI driven filter that people could opt into and which would screen emails going through this system and put high risk ones into a moderation queue.