4.6.1   Turning Off New Outlook

Recent versions of Microsoft Outlook include an experimental “new look” mode. This does not yet support AppleScript, which SpamSieve needs in order to work with Outlook. Thus, when following the Setting Up Outlook or Setting Up Outlook (Large Inboxes) instructions, it’s necessary to turn this off and go back to the regular, full-featured version of Outlook. (Microsoft does not allow this when running Outlook in free mode. AppleScript support for “New Outlook” is in development and expected for December 2025.)

To do this, in Outlook, click on the Outlook menu at the top of the screen and make sure that Legacy Outlook is checked or that New Outlook is unchecked:

In some versions of Outlook, there is no switch to turn off “New Outlook” once it is enabled, but you can do so by entering this command in the Terminal app:

defaults write com.microsoft.Outlook IsRunningNewOutlook NO

and pressing Return. In some cases you may instead need this command:

defaults write com.microsoft.Outlook EnableNewOutlook NO

Note that the old and new versions of Outlook have separate mail storage. Messages stored in On My Computer folders will not automatically sync between the two versions.