What happens to emails placed into the iCloud Mail Junk Folder.
For example: Nothing happens, they are just stored in that folder.
OR
Placing mail into the Junk folder means any future mails from the same sender are automatically sent to the junk folder.
That mean the sender has been either identified by a Mail Rule the user has setup is working or the user has identified the sender ( without any Rules setup ) as junk.
It also mean the sender s e-mail may or may not continue to be put to Junk Folder for any new e-mails received form that sender.
Block or unblock senders in Mail on Mac
I understand how to set up rules in Mail, but I can't find any rules in iCloud Mail
iCloud Mail Junk Folder
