Apparently after an upgrade of either Outlook and/or SpamSieve when having selected a mail and training SpamSieve, it does not work anymore (i.e. it doesn’t move the mail to junk for example), used to work fine for a very long time.
I am referring to this functionality:
To train SpamSieve with spam messages, select one or more of them and then choose SpamSieve - Train as Spam from the Script menu.
To train SpamSieve with good messages, select one or more of them and then choose SpamSieve - Train as Good from the Script menu.