Summary
Before November 1, 2026, to keep filtering your mail with SpamSieve, you 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, November 2025, New Outlook does not have support for AppleScript, and thus it cannot work directly with SpamSieve.
You can choose Give Feedback from the Help menu in Outlook to ask Microsoft to prioritize support for AppleScript so that New Outlook will work directly with SpamSieve as soon as possible.
Legacy Outlook vs. New Outlook
SpamSieve has worked with Microsoft Outlook and its predecessors since its inception. 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, 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 since 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 is 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 statemens 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. We expect that, by the time this happens, New Outlook will support AppleScript and the current version of SpamSieve at that time will seamlessly keep working with it.
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 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 16.102.1, 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.
How Can I Use SpamSieve With New Outlook Now?
If you’d like to use New Outlook before it supports AppleScript, 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. (This works for IMAP and Exchange accounts, but not for POP accounts.) You can hide Mail or run it without any windows open so that the filtering happens invisibly in the background (though you’ll need to remember to launch Mail when you restart your Mac). You do not have retrain SpamSieve from scratch; it will keep using the same training data from when you were using it with Outlook. Going forward, if you need to correct any filtering mistakes you can train SpamSieve directly from Outlook by moving messages into the special TrainSpam or TrainGood mailbox. To do this, first make sure that Train messages in TrainSpam and TrainGood is selected in the Settings ‣ Apple Mail ‣ Training window. There’s more information about how this works in the Drone Setup and Remote Training section of the manual.
When Will SpamSieve Work Directly With New Outlook?
Microsoft’s roadmap currently has AppleScript support expected to roll out in December 2025. At that time, the current version of SpamSieve may automatically start working with Outlook again. We will test with beta versions of Outlook as they become available and update SpamSieve as necessary.
Support for rules is also not implemented yet, and it is not currently on Microsoft’s roadmap, but this is not required for SpamSieve support. Legacy Outlook had a performance bug that required a different SpamSieve setup if you had a large number of messages in your inbox, and in some cases this required using Outlook’s rules feature. It’s unclear what the performance characteristics of New Outlook’s AppleScript support will be and, thus, whether rules support will be required for large inboxes. Many mail providers support server-side rules, which is good enough for SpamSieve’s purposes.
You can choose Give Feedback from the Help menu in Outlook to ask Microsoft to prioritize support for AppleScript, rules, or any other features that you miss.