Outlook for Mac Not Connecting to Exchange Online: What to Do About Legacy Outlook (2026)

Short answer: According to Microsoft's support page "End of support for legacy Outlook for Mac" (reviewed 2026-10-25), starting October 2026 the legacy Outlook for Mac client stops working against Exchange Online mailboxes. The documented fix is to switch to the new Outlook for Mac by turning off the "Legacy Outlook" toggle, or to update the app if you do not see the toggle. Your mail is not deleted; it stays on the server.

Last reviewed: October 25, 2026.

What is happening, in plain English

For years, Outlook for Mac had two looks: the older "legacy" Outlook, and the redesigned "new Outlook" with a toggle in the top corner to switch between them. The legacy app talks to Microsoft 365 mailboxes using a protocol called Exchange Web Services, or EWS. Microsoft's support page states: "Legacy Outlook for Mac uses Exchange Web Services (EWS) in Exchange Online to deliver your email."

The same page says EWS in Exchange Online is retired on October 1, 2026, and that "starting October 2026, the legacy Outlook for Mac client will stop working against Exchange Online mailboxes." The new Outlook for Mac does not depend on that protocol, which is why switching to it is the recommended path.

What Microsoft has not published

The support page does not list a specific error message and does not describe an authentication change. We therefore cannot tell you the exact wording you will see. The symptoms people typically report when a mail connection fails are covered in the "Common symptoms" section below, and they are described as symptoms, not as documented error codes.

Some institutions publishing their own notices describe a phased approach, with a permanent EWS shutdown on April 1, 2027. We could not confirm that date on a Microsoft page we could open, so treat it as unconfirmed. What is confirmed is the October 2026 date for legacy Outlook for Mac.

Am I affected? A quick decision table

Your situation	Affected?	What to do
Legacy Outlook for Mac connected to a work or school Microsoft 365 mailbox (Exchange Online)	Yes, per Microsoft	Switch to new Outlook or update
Legacy Outlook for Mac connected to Exchange on-premises (your company runs its own server)	No, supported until October 9, 2029 (security updates only)	Ask your admin about long-term plans
New Outlook for Mac (legacy toggle off)	Not by this change	Keep it updated
Outlook on the web (outlook.office.com) in a browser	No	Works as a fallback
Outlook on Windows	Not covered by this Mac notice	See our Windows support page if you need help

Personal Gmail, iCloud or other IMAP accounts added to legacy Outlook are a different case. Microsoft's page speaks specifically about Exchange Online mailboxes, so we do not claim anything about other account types here.

How to check your Outlook version

1. Open Outlook for Mac.
2. In the menu bar choose Outlook > About Outlook. Note the version and whether it says Microsoft 365, 2024, 2021 or 2019.
3. Look at the top right of the Outlook window. If you see a toggle labelled Legacy Outlook that is switched on, you are using the legacy interface. If the toggle is off, or the window looks like the redesigned app, you are already on the new Outlook.
4. Open Outlook > Settings > Accounts (the label can vary slightly by build) and check whether your work address is listed as an Exchange account.

If you are not sure whether your mailbox is "Exchange Online" or on-premises, ask whoever manages your email. If your company uses Microsoft 365 for email, it is almost certainly Exchange Online.

Common symptoms when legacy Outlook cannot reach Exchange Online

These are general symptoms of a failed mail connection, not Microsoft-published error codes for this change. If you see them in legacy Outlook after October 2026, the end-of-support change is a likely cause worth ruling in or out first:

• New mail stops arriving, and the bottom status bar shows "Disconnected" or "Working offline".
• Outlook keeps asking for your password even though it is correct.
• The folder list does not refresh, and sent messages sit in the Outbox.
• Calendar invitations and contacts stop updating.

Before blaming the change, rule out the ordinary causes: no internet, an expired password, or a sign-in blocked by your organization. Our general guide to Outlook not working walks through those checks.

Step 1: Back up first (export to an .olm file)

Back up before you switch or reinstall anything. For Exchange Online accounts your mail also lives on the server, but a local export protects local-only folders and gives you a safety copy. Microsoft documents the export in "Microsoft's export article for legacy Outlook for Mac". The feature exists in the legacy client, so do this before you leave it.

1. In legacy Outlook for Mac, find the Export option. Menu locations vary by version, so follow Microsoft's export article for your build.
2. In the "Export to Archive File (.olm)" box, tick the items to include and click Continue.
3. In the "Save archive file as" box, pick a location such as Downloads and click Save.
4. When the completion notification appears, click Finish.

Microsoft documents exporting to an .olm archive file in legacy Outlook for Mac. Copy the finished file to an external drive or another location, not just the same Mac. Microsoft points to a separate article, "Import email messages, contacts, and other items into Outlook for Mac", for restoring from an .olm file. For a broader backup plan for a small office, see our cloud backup guide for businesses.

Step 2: Switch to the new Outlook for Mac

This is the first fix Microsoft documents. Per the support page:

1. Open legacy Outlook for Mac.
2. Turn off the Legacy Outlook toggle.
3. Follow the prompts. The new Outlook uses your existing accounts and signs you in again if needed.

Expect a different layout and some changed menus. Take ten minutes to confirm your signature, rules, calendar and shared mailboxes look right. Feature differences between the two apps exist, and Microsoft's page does not list them, so we do not claim which features are missing. If something you rely on is gone, tell your admin before you decide anything else.

Step 3: If there is no toggle, update the app

Microsoft says that if you do not see the toggle, you should update through Help > Check for Updates, or download the latest app from the Apple App Store. Install every offered update, restart Outlook, and check again.

Step 4: Use Outlook on the web as a stopgap

If you need your mail right now and the switch is blocked, sign in at outlook.office.com with your work account in Safari or Chrome. It does not rely on the legacy Mac app, so you can read and send mail, check your calendar and keep working while the Mac client is sorted out. This is a workaround, not a long-term setup, and your organization may restrict it.

What to tell your IT admin

If you work for a company, your administrator controls part of this. Microsoft's page says the app "will continue to respect admin preferences" for enabling the new Outlook, so an admin policy could be what keeps you on the legacy app. Send them a short message:

• Which Mac, macOS version and Outlook version you use (from Outlook > About Outlook).
• That you rely on legacy Outlook for Mac with an Exchange Online mailbox, and Microsoft says it stops working from October 2026.
• Whether the new Outlook is allowed by policy, and whether any add-ins, shared mailboxes or delegate access you use need testing.
• The date you want the change done, and that you have a backup.

Administrators should also know that EWS in Exchange Online is being retired, according to Microsoft. Other apps and integrations that use EWS can be affected too. Some university notices report that Apple Mail uses EWS when connected to Exchange Online, but we could not confirm that on a Microsoft page, so check with your admin before relying on Apple Mail for a work mailbox.

Small business checklist

1. List every Mac that connects to Microsoft 365 mail, with its Outlook version.
2. Identify which ones still have the Legacy Outlook toggle on.
3. Export an .olm backup from each before any change.
4. Switch one pilot Mac first and check signatures, rules, shared mailboxes and calendars.
5. Roll out to the rest and keep Outlook on the web as a fallback.
6. Document the new setup, including which device uses which account.

If you would rather not do this alone, a technician can walk through it with you over a remote session. See our remote Mac support, Outlook email setup help or remote repair pages.

Common mistakes

• Uninstalling Outlook before exporting. Export first.
• Deleting the account to "fix" it. This can remove local data. Back up, then change one thing at a time.
• Assuming the problem is the password. Repeated resets will not help if the client itself is no longer supported.
• Waiting for it to fix itself. Microsoft's page describes an end of support, not a temporary outage.

Frequently asked questions

Why is Outlook for Mac not connecting to Exchange Online?

If you use the legacy Outlook interface, Microsoft says it stops working against Exchange Online mailboxes starting October 2026. Other causes include no internet, a changed password or a blocked sign-in, so check those too.

Which Outlook for Mac versions are affected?

Microsoft lists Outlook for Microsoft 365 for Mac, Outlook 2024, Outlook 2021 and Outlook 2019 for Mac when used as legacy Outlook.

Will I lose my email?

Microsoft's page does not say mail is deleted. Exchange Online mail is stored on the server, but we still recommend an .olm export first.

How do I know if I'm on legacy Outlook?

Open Outlook > About Outlook for the version, and look for the Legacy Outlook toggle at the top right of the window. If it is on, you are on legacy.

Does this affect Exchange on-premises mailboxes?

According to Microsoft, legacy Outlook for Mac continues to work with Exchange on-premises mailboxes, receiving security updates only through October 9, 2029.

There is no Legacy Outlook toggle. What now?

Use Help > Check for Updates, or download the latest Outlook from the Apple App Store, as Microsoft advises. If your admin has blocked the new Outlook, contact them.

Can I keep using Outlook on the web?

Yes, as a stopgap. Outlook on the web in a browser is not the legacy Mac app, so this change does not apply to it.

Where can I get help from Microsoft?

For help, use Help in the app or contact your organization's help desk.