Organizations that still use the older Outlook for Mac interface should plan a controlled migration. Microsoft says legacy Outlook for Mac will stop connecting to Exchange Online mailboxes starting in October 2026. Exchange Online is the mailbox service commonly used for business email through Microsoft 365.
The current Outlook for Mac remains supported, but switching is more than a user-interface change. Any data stored only on a Mac, along with workflows that depend on specific Outlook features, should be reviewed before the change.
Why the connection is being retired
Legacy Outlook connects to Exchange Online through Exchange Web Services, commonly called EWS. Microsoft is retiring that connection method through a phased process beginning in October 2026.
An IT administrator may be able to extend legacy access temporarily after October 2026, but Microsoft plans to shut down EWS completely on April 1, 2027. If an organization uses an extension, it should still set a firm internal date for completing the migration.
Identify Macs that still use legacy Outlook
Installing an Outlook update does not necessarily switch the application to the current experience. In the Outlook window, look for an enabled Legacy Outlook switch. Turning it off moves the application to the redesigned Outlook experience.
The Help menu provides another check. If it includes Revert to Legacy Outlook, the newer interface is already active. If neither control appears, the user should ask the organization’s IT administrator or provider which Outlook version and mode are in use.
Determine whether the deadline applies
The relevant date depends on the Outlook license and where the mailbox is hosted:
Microsoft 365 business email: Users with Exchange Online mailboxes need to move from legacy Outlook to the current Outlook.
Microsoft 365 Personal or Family: Legacy Outlook support ends in October 2026. The Exchange Online cutoff does not establish a disconnection date for third-party accounts such as Gmail or iCloud.
Exchange Subscription Edition on organizational servers: Microsoft lists legacy support through October 9, 2029, with security updates and technical assistance provided on a best-effort basis.
Office LTSC 2024: Microsoft lists the same limited support through October 9, 2029. However, legacy Outlook will still lose access to Exchange Online when EWS is shut down.
Organizations that are uncertain where their work email is hosted should verify that detail with their IT provider before scheduling the change.
Protect information stored on the Mac
Begin with a current backup of the Mac. Then inspect Outlook for information stored only on that computer, especially folders under On My Computer. Local calendars, contacts, and previously imported archives deserve particular attention. Signing in to the same account on another device will not restore information that exists only on the original Mac.
Legacy Outlook can also export messages, contacts, and other items to an .olm archive. Depending on the version, begin with Export on the Tools tab or use the File menu. Store the completed archive in a location included in the organization’s backups.
Microsoft’s migration guidance says local tasks and notes are not transferred. Its current feature comparison lists the in-app Notes and Tasks modules as upcoming and Public Folders as unavailable. Users who depend on those features should establish another way to access the information before switching.
Move to the current app
After backing up data and reviewing required features, turn off the Legacy Outlook switch. If the switch is unavailable, use Help > Check for Updates. On a company-managed Mac, the user should involve IT if the switch or update option is unavailable.
If local folders do not appear, look for Import On My Computer Data in the File menu or an Import Now button under On My Computer. Microsoft documents both import paths. Menu wording can vary by version, so users should get assistance before deleting or recreating an Outlook profile if neither option appears.
Test business-critical workflows
After switching and completing any local import, verify the following:
Accounts: Confirm that expected folders and recent messages appear. Send a test message and verify that a reply arrives.
Calendars and contacts: Review upcoming appointments and confirm access to shared calendars and important contacts.
Local archives: Open several older messages and their attachments. Keep the original data and backups until the migration has been verified.
Essential features: Check signatures, important rules, shared mailbox access, and required add-ins.
When something fails, document the task being attempted, the result, and any error message for the help desk or IT provider. For example, identify the shared mailbox that cannot be opened. Microsoft directs personal-account users to Help > Contact Support.
If the organization offers Outlook on the Web, confirm that users can sign in and use it as a fallback when the desktop app has problems. Outlook on the Web does not replace access to information stored locally on a Mac.
For businesses with managed Macs, treating this as a staged endpoint-management change can reduce disruption: identify affected users, preserve local data, test shared resources, and set an internal completion date before the final EWS shutdown.
(Featured image by iStock.com/Rawf8)
