Smart Mailbox filter "Message is not in mailbox" for iCloud mailboxes When I create or edit a Smart Mailbox and I want to add filter Message is not in mailbox it works fine for all my e-mail accounts except iCloud.

So, if I add such filter in some Smart Mailbox settings and would try to add some mailbox from my iCloud account, it will do that, but it will reset it after I press OK - when I open settings for this Smart Mailbox again, I see the following:



As you can see, instead of my chosen mailbox that I wanted to exclude there is No mailbox selected. And of course this filter doesn't work.

But again, if I add any mailbox from any other account beside iCloud to this filter, it works fine, so the issue is only with iCloud mailboxes.

Do you know, why is that and how to fix this?
I had the same problem and I found a solution here luckily after searching like crazy. The problem was, that I used my Gmail account as my Apple ID, so mail got confused. After I deactivated mail in my iCloud account settings, it was working fine. This is obviously only a solution if you don't use both accounts. Anyway, maybe it helps someone:


  And here's the solution, or rather the explanation for the problem: If
  you're using your gmail Adress as your apple-id (and therefore as your
  login credentials for your iCloud account) Apple Mail seems to get
  confused. Simply change your iCloud Username to something else and
  your good to go.