Microsoft Outlook 2016 (currently available as part of Office 365) removes the Run AppleScript rule action feature. This makes it impossible to create a rule that automatically processes incoming messages with SpamSieve, as has been possible since SpamSieve 1.0 and Microsoft Entourage and Outlook Express in 2002.
The Office 2016 applications have been designed to run in the Mac OS X App Sandbox. Microsoft’s legacy AppleScript code didn’t work with the sandbox. It was easier to remove the Carbon-era code that was no longer working than to adopt Mac OS X 10.8’s NSUserAppleScriptTask API, which Apple Mail and other applications use to run AppleScripts from the sandbox.
Is there a workaround?
The Setting Up Outlook 2016 section of the manual describes some ways that you can still use SpamSieve with Outlook 2016. However, this is much less smooth than with previous versions.
What can I do?
Bringing the Run AppleScript feature back is on Microsoft’s to-do list, but it’s not a top priority due to low perceived customer usage. The most important thing to do is to use the “send-a-smile” button in Outlook’s main window (below the search field) to send Microsoft feedback, asking them to prioritize this feature. This also works from the free Office 2016 preview. You can also vote in the Outlook Suggestion Box.