Legacy Outlook for Mac End of Support (October 2026): What Changes and How to Protect Emails
If you still have Outlook for Mac open and “Legacy Outlook” is switched on, then this is the month that will ultimately change the way you use this email client. Microsoft announced that legacy Outlook for Mac will stop working with the Exchange Online (Microsoft 365) mailboxes in October 2026 — and from then on, the legacy client will no longer be able to send or receive emails for your work/school/personal Microsoft 365 account.
And this guide gives you all the necessary information on what is changing, who is affected, why Microsoft is doing this, and most importantly — the one step everyone is missing when they cancel their Legacy Outlook for Mac subscription, which is to back up their local mailbox before doing so.
Quick Answer
- What is ending: The Legacy (classic) Outlook for Mac client’s connectivity to Exchange Online mailboxes
- When is it ending: October 2026.
- Who is affected: those who are using legacy Outlook on their Mac computers and have Microsoft 365, Outlook.com, or Exchange Online accounts
- Who is getting more time: organisations running Exchange On-Premises and Office LTSC 2024 users get security updates through October 9, 2029.
- What to do: export your mailbox and then turn off the Legacy Outlook switch to move to the new Outlook for Mac client.
What is Legacy Outlook for Mac?
“Legacy Outlook for Mac” is Microsoft’s name for the classic Outlook client that comes with Outlook 2019, 2021, and 2024 for Mac and Microsoft 365. When Microsoft unveiled the redesigned “new Outlook for Mac,” it kept the old client within the same app behind a switch. This switch lets you switch between the two versions, and is why many people didn’t realise they were using the old Outlook.
You are on legacy Outlook if:
- The Legacy Outlook (or “New Outlook”) switch is there and set up so that the classic interface is visible.
- You still use On My Computer folders to keep your archived mail local.
- Your Outlook looks the same as it did a few years ago, with the old ribbon and sidebar.
Legacy Outlook for Mac End of Support: Why Microsoft Is Ending It
The short answer is Microsoft’s retirement of Exchange Web Services (EWS). Legacy Outlook for Mac uses EWS to communicate with Exchange Online and provide the user with their email. EWS is an older protocol which Microsoft is retiring in Exchange Online in favour of Microsoft Graph and newer synchronisation technology used by the new Outlook.
Once it is turned off on a mailbox, legacy Outlook has no means of communication anymore. That is why the cut-off is dictated by the Exchange Online side and has nothing to do with your Mac or its macOS version. The same logic applies to why Exchange On-Prem users get until 2029 to migrate – their servers still host EWS.
The practical implications are the same either way – the classic client will no longer be under development or supported for Microsoft 365 mailboxes.
What happens If You Keep Using Legacy Outlook?
When your account is on Microsoft 365 or Exchange Online, here is what you will experience when the date of the end of support for your mailbox is reached:
- Mail will cease to synchronise. The client will no longer be able to establish a connection to your mailbox, thereby ceasing the two-way synchronisation of mail.
- Calendar and contact data will stop updating, thereby causing inconsistencies in meeting details and missed information about new contacts.
- You can switch back temporarily. Microsoft allows users to return to Legacy Outlook via Help > Revert to Legacy Outlook in supported versions.
- No New Update. Although legacy Outlook may still function in some features at the time of the switch, no new features will be introduced, and only critical security updates will be provided.
If your organisation is running Exchange On-Premises, legacy Outlook functionality will be available until 9th of October, 2029. However, please note that it will only receive security updates and no other form of support. This does not constitute a long-term solution.
How Legacy Outlook for Mac End of Support Affects Local Mail Data
Almost all of your mail is safe because it’s stored on Microsoft’s servers. Outlook will recognize it and copy it to the new app. The only exception is mail stored in On My Computer folders. These are local Outlook folders that were created on your Mac by the legacy Outlook app. This might be because you imported a PST or OLM archive a long time ago or moved old messages from the server to save space on the mail server.
The new Outlook for Mac has never supported On My Computer folders. When you try to turn on the new Outlook app, it warns you that these folders will not be migrated. The data is not deleted, but it is no longer available. If you can no longer access Outlook with your account, you will not be able to open a local archive.
Before migrating, check if you have any On My Computer folders:
- Open legacy Outlook.
- On the left, look for a section called On My Computer.
- If it’s not there, go to Outlook> Settings> General and make sure Hide On My Computer folders is not selected.
If you find any items in these folders, back them up right away. The same goes for any local calendars and contacts saved under On My Computer.
Back up Legacy Outlook for Mac Before You Switch
An OLM file is the proprietary Outlook for Mac archive format that stores email, contact, calendar, task, and note data in one convenient file, making it the recommended option for performing a backup prior to any migration.
Method 1: Export an OLM file from legacy Outlook
- Open legacy Outlook for Mac
- Go to File > Export (Tools > Export in some versions)
- Select the items to include. For a full Outlook backup, select all.
- Click Continue and select where you would like to save the .olm file; an external hard drive is recommended. Make sure you remember the location of the file and keep it somewhere safe!
Complete this process while legacy Outlook for Mac can still open your account. This is the only native way to export On My Computer folders to a portable archive file.
Method 2: Convert the OLM File to Use it Anywhere
As such, an OLM file is only a backup copy. The new Outlook for Mac cannot open On My Computer data in the way the legacy Outlook could, nor can Windows Outlook, Apple Mail, Thunderbird, or Gmail read OLM files at all. In order to actually utilise that archive, it needs to be converted. You can use a dedicated tool, OLM Converter, that can easily process the Mac Outlook files and convert them to any desired format:
Convert Outlook for Mac to files that can be opened by other apps:
- PST for Outlook on Windows or the new Outlook (see how to export Outlook for Mac to PST).
- MBOX for Apple Mail and Thunderbird.
- PDF for a readable long-term archive.
- vCard and ICS for contacts and calendars.
- Direct migration to Gmail, Office 365, Thunderbird, and other accounts.
How to Switch From Legacy Outlook to the New Outlook for Mac
Once the backup is completed, you can proceed to switch to the new client within a short period of time:
- Make sure Outlook is updated to the latest version. Go to Help > Check for updates (Microsoft AutoUpdate).
- Launch legacy Outlook for Mac.
- Toggle off the Legacy Outlook switch.
- Outlook will restart in the new interface and synchronise the mailbox data with the server.
- Wait for the mail, calendar, and contact data to be downloaded from the server (it may take longer for large mailboxes).
- Verify that all folders, rules, signatures, and shared calendars were migrated successfully. If some items are missing, recreate them in the new application.
If the toggle is disabled or unavailable, it means that you have successfully switched to the new Outlook. Your mailbox data stored on the server will start appearing in the new interface. To access local data (OLM files), you will need to use either the converter or another email client (if available).
FAQs
Q) Is legacy Outlook for Mac supported?
A) No longer for Microsoft 365 or Exchange Online mailboxes. It will stop being supported with Exchange Online in October 2026 and with Exchange On-Premises or Office LTSC 2024 – October 9, 2029.
Q) Why is legacy Outlook for Mac not working?
A) The most common reason your Outlook for Mac has stopped syncing in October 2026 is that you are trying to access an Exchange Online mailbox via Exchange Web Services, which has been deprecated. To resolve this issue, switch to the new Outlook for Mac.
Q) Can I switch back to legacy Outlook for Mac?
A) No, once you switch to the new version of Outlook for Mac, you cannot go back to the older version.
Q) Will I be able to get all my emails after switching to the new Outlook?
A) Your mailbox data stored on the server will be available again in Outlook for Mac after you log in to your account. However, emails saved in On My Computer folders will no longer be accessible in the new Outlook. Hence, make sure to save those emails locally as an OLM file.
Q) How do I open OLM files in Outlook for Mac without legacy Outlook?
A) You can convert your OLM files to PST, MBOX, PDF, or other formats with the help of OLM Converter or migrate them directly to Gmail, Thunderbird, or Office 365. For quick access, use the OLM File Viewer.
Q) Does this apply to Outlook on Windows too?
A) No, this update only affects Outlook for Mac. Outlook on Windows will continue to operate normally.
Conclusion
Legacy Outlook for Mac End of Support is no longer a concept of the future but a present reality. Microsoft’s Legacy Outlook for Mac retirement is now in place for Exchange Online users in October 2026. The transition to the new Outlook is quick and leaves behind your server mail but spares the data stored on My Computer, which requires your attention. Export an OLM backup today while legacy Outlook is still active. If you ever need to access this archive in another application or on another platform, the recommended tool will help you convert it to PST, MBOX, PDF, or directly migrate it, preserving the folder structure as well as attachments.