Summary
Before November 1, 2026, to keep filtering your mail with SpamSieve, most users will need to either switch from Legacy Outlook to New Outlook or switch to another mail client (such as Apple Mail). As of this writing in August 2026, New Outlook does not have much support for AppleScript, and thus it cannot work directly with SpamSieve. The exception is if you had purchased Outlook through Microsoft’s LTSC (Long Term Service Channel), in which case Outlook will continue to fully support AppleScript and SpamSieve until October 2029.
Legacy Outlook vs. New Outlook
SpamSieve has worked with Microsoft Outlook and its predecessors since its inception in 2002. This was possible because of their strong support for AppleScript. This macOS technology let SpamSieve access the contents of your e-mail messages (so it could determine whether they were spam), see which messages you had selected for training, and it also let SpamSieve tell Outlook to move the spam ones to the Junk Email folder.
In October 2020, Microsoft introduced a new version of Outlook built on Web technologies. Many popular features were missing, including AppleScript and rules. Microsoft said that it would continue to support both the current and new versions of Outlook, as separate modes within the same app, while it worked on bringing the new version up to feature parity. Initially, there was a switch to let you opt in to preview the “New Look” version. In recent years, the new version was the default and there was a switch to go back to “Legacy Outlook.” Running in legacy mode has been required for compatibility with SpamSieve because the new mode has not yet restored AppleScript support (nor added another mechanism to provide equivalent functionality).
Ending Support for Legacy Outlook
Microsoft has announced that, as of November 1, 2026, it will be ending support for Legacy Outlook. This was originally scheduled for November 1, 2025, but on October 6 Microsoft extended the date by a year, in keeping with its previous statements that Legacy Outlook support would continue until AppleScript support had been restored to New Outlook. After November 1, 2026, when you launch Outlook on your Mac, it will force you to migrate to New Outlook.
AppleScript Support in New Outlook
Starting in 2020, Microsoft had consistently said that it would bring AppleScript support to New Outlook. We had planned to update SpamSieve as necessary to work with the new AppleScript support when it arrived. On August 12, 2026, Microsoft announced a change in plans:
We have decided not to move forward with this feature. We apologize for the inconvenience.
With no AppleScript support and no other means of automating Outlook, it will not be possible for SpamSieve to directly integrate with New Outlook.
Which Outlook Versions Are Affected?
Microsoft’s support page says that Legacy Outlook will no longer be supported for Microsoft 365 subscriptions (personal, family, business, and enterprise) or for the standalone version of Outlook 2024. If you purchased Outlook LTSC (Office Long Term Service Channel), support will continue until October 2029. We believe, but cannot guarantee, that older versions of Outlook such as 14.x and possibly early versions of 15.x from before Outlook was subscription-based may continue to work. As of this writing, the current version of Outlook is 16.112.1, which includes the switch for changing between Legacy Outlook and New Outlook. However, Microsoft has said that, even if you keep this version installed and don’t update it, and even if you have an active Microsoft 365 subscription, the legacy mode will stop working on November 1, 2026.
What Can I Do?
Continue Reading Your Mail in Outlook, But Filter It Using Apple Mail
You can still use SpamSieve to filter your Outlook e-mail even though SpamSieve will no longer be able to directly communicate with Outlook. All Macs include Apple’s Mail app, and it works great with SpamSieve. If you add your mail accounts to Apple Mail and set up SpamSieve for Apple Mail, SpamSieve and Mail will filter your inbox, and the spam messages will automatically be removed from your Outlook inbox, too.
Switch to Another Mail Client
There are a variety of native Mac mail clients that work with SpamSieve and remain in active development: Apple Mail, Airmail, GyazMail, MailMate, MailMaven.
Send Feedback to Microsoft
We hope that Microsoft will change its mind about AppleScript or add another plug-in or extension mechanism. You can choose Give Feedback from the Help menu in Outlook to ask Microsoft to prioritize this (or other features like rules that you miss).