I have Outlook for Mac 16.16.18 that I use for one of my email addresses. I have installed the Outlook - Filter Mailboxes script and it sits ope on my Dock, but SpamSieve consistently puts a few of my good messages into the Junk folder. Messages from the same senders go to Junk again and again. I have tried to Train as Good from the Scripts icon in the desktop menu bar. I have tried to tell Outlook that the message is Not Junk by clicking on that option in the Outlook menu bar. I have written server rules to tell Outlook to move those messages to the Inbox. I have written client rules to Change the Status to Not Junk and to move the messages to the Inbox. None of these have worked.
I should have noted that my computer is running Mojave 10.14.6
It’s unlikely to be SpamSieve doing this because by default it whitelists senders that you train as good, along with senders that are in your Contacts. Perhaps a server filter is moving the messages there. The Why do good messages keep going to the Junk or Spam mailbox? section of the manual describes how you can figure this out.