I was reminded a few days ago that the Legacy version of Outlook for macOS will not be supported after October 2026. I tried the New Outlook a few times over the past few years, but there always seemed to be a feature or two missing, so I’m still on the Legacy version. If you are using the Legacy version, you should start planning to switch to the New version.
Aside from no longer receiving security updates, the biggest issue with Legacy Outlook is that connections to cloud-based Exchange servers, including Office 365 subscriptions, will fail.
From what I’ve been able to gather, the main serious problem that people have encountered with moving from Legacy Outlook to New Outlook is that sometimes the local “On My Computer” emails don’t appear after switching. If you are using Legacy Outlook, be sure to export your data to an OLM file before switching to New Outlook. If your local emails fail to appear, you’ll be able to restore them from the OLM file.
Note: once you switch from the Legacy version to the New version, you no longer can revert to the Legacy version.
Also, if you use Rules to manage files in Local Folders, they likely will break. Local contacts are no longer supported, so you will need to use cloud-synced contacts. There also appear to be reductions in configurability for POP accounts. I haven’t switched yet, so I can’t verify any of the above.
If you are unsure of whether you are still on the Legacy version or have already moved to the New version of Outlook, look for a “Legacy Outlook” toggle switch in the upper right corner of the app. It only will appear in Legacy Outlook.
By the way, I also noticed that the New Outlook is scheduled to begin supporting exporting of mail archives in PST format with the September release.