If Apple Mail suddenly stopped syncing with Microsoft 365, I would not immediately assume the password is wrong.
Microsoft currently confirms an issue where some Microsoft 365 email accounts are being disconnected from Apple Mail. The first recommended fix is to sign in again. If that fails, Microsoft recommends removing the Exchange account from Apple Mail and adding it again. On macOS, however, there is now a second possible cause: beginning in October 2026, some Exchange organizations may need an administrator-side EWS configuration change before Apple Mail can sync again.
That distinction is important because repeatedly deleting and re-adding the account will not solve an Exchange configuration problem controlled by your company.
Quick Fix: Sign In to Microsoft 365 Again
I would start with the least destructive fix.
Microsoft says users affected by the current Apple Mail disconnection issue should first re-enter their Microsoft 365 credentials.
If Apple Mail displays a sign-in or account warning, use that prompt and authenticate again with the Microsoft 365 account.
If you do not see a prompt, check the Mail account settings manually.
On current Apple devices, the path is generally:
Settings → Apps → Mail → Mail Accounts
Open the affected Exchange account and complete any requested authentication.
If Mail starts syncing again after that, I would stop there.
There is no reason to remove the entire account if a fresh authentication fixes it.
Fix 2: Remove and Re-Add the Exchange Account
If signing in again does not work, Microsoft’s next recommended step is to remove the Microsoft 365 Exchange account from Apple Mail and add it again.
The current process is:
- Open Settings
- Go to Apps → Mail
- Open Mail Accounts
- Select the affected Exchange account
- Choose Delete Account
- Return to Mail Accounts
- Select Add Account
- Choose Microsoft Exchange
- Sign in again with your Microsoft 365 credentials
Before doing this, I would make sure the account really is hosted in Microsoft 365 or Exchange and that the user knows the correct login details.
Removing an Exchange account from the device does not normally delete mail stored in Microsoft 365 itself, but locally cached account data will be removed from the device and downloaded again after the account is added.
If That Still Does Not Work on macOS, Stop Repeating the Same Fix
This is where the October 2026 change becomes important.
Apple published new guidance on October 13, 2026 for users who can no longer sign in to Microsoft Exchange on macOS or whose Mail, Calendar, Contacts, Notes or Reminders have stopped syncing.
Apple says affected users should contact their Exchange administrator.
That means the problem may no longer be on the Mac itself.
Microsoft has been moving Exchange Online away from Exchange Web Services, or EWS, and Apple says organizations that still need EWS beyond October 2026 must verify that EWS is enabled and allow Apple Internet Accounts in their EWS configuration.
If this is the cause, changing your password, restarting Mail or repeatedly deleting the account will not fix the underlying problem.
The Administrator Fix
Apple provides a specific application ID that Exchange administrators may need to allow:
Apple Internet Accounts App ID:f8d98a96-0999-43f5-8af3-69971c7bb423
Apple says Exchange administrators should confirm that EWS is enabled for the organization and add Apple Internet Accounts to the organization’s EWS allow list where required.
This is therefore not a normal end-user troubleshooting step.
If you use a work or school Microsoft 365 account and Apple Mail stopped working around October 2026, I would send the IT administrator something like:
“Apple Mail can no longer sync my Microsoft Exchange account. Apple says organizations may need to allow Apple Internet Accounts for EWS after the October 2026 Exchange Online change.”
That gives the administrator something useful to investigate instead of simply receiving “Mail does not work.”
Why Is This Happening?
There are actually two issues that can look almost identical.
The first is the current Microsoft 365 disconnection problem.
Microsoft explicitly says some Microsoft 365 email accounts are being disconnected from Apple Mail and that Microsoft is aware of the issue.
The second affects Exchange integration on macOS as Microsoft moves away from Exchange Web Services.
Apple says that beginning in October 2026, affected organizations may need to configure EWS access correctly for Apple Internet Accounts.
From the user’s perspective, both problems may look the same:
- Mail stops updating
- Exchange asks for a password again
- sign-in fails
- Calendar stops syncing
- Contacts stop updating
- the account appears disconnected
But the solutions are very different.
How I Would Diagnose It
I would use a very simple order.
1. Check whether Microsoft 365 works in the browser
Sign in to Outlook on the web.
If the account works there, the Microsoft 365 account itself is probably still active.
That immediately makes an Apple Mail configuration or authentication problem more likely.
2. Re-enter the credentials in Apple Mail
This is Microsoft’s first recommended fix.
If it works, the problem was probably just the disconnected authentication session.
3. Remove and re-add Exchange
If authentication still fails, recreate the account using Microsoft Exchange, not a generic IMAP configuration.
Microsoft specifically recommends removing and re-adding the Exchange account when reauthentication does not fix the disconnection.
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4. Check whether other company users are affected
If several Mac users in the same Microsoft 365 organization suddenly have the same problem, I would immediately suspect an administrator-side configuration issue.
At that point, repeatedly troubleshooting every Mac individually makes little sense.
5. Escalate the EWS configuration to IT
For macOS failures appearing after the October 2026 Exchange changes, ask the Exchange administrator to check the EWS configuration and Apple Internet Accounts allow-list requirement documented by Apple.
What About iPhone and iPad?
I would not automatically assume the October 2026 macOS EWS issue applies identically to iPhone and iPad.
Apple’s October support notice specifically addresses macOS.
Microsoft’s separate Apple Mail disconnection guidance, however, uses the current Mail account settings flow and recommends reauthentication or removing and re-adding Microsoft Exchange.
So on an iPhone or iPad, I would begin with Microsoft’s reconnect steps.
I would only escalate to organization-side Exchange troubleshooting if the normal account fixes fail or multiple users are experiencing the same problem.
Should I Switch to Outlook Instead?
Possibly as a temporary workaround, but I would not describe that as the actual fix.
If the Microsoft 365 account works correctly in Outlook while Apple Mail does not, that is useful diagnostic information.
It tells me the mailbox itself is probably fine.
But if I prefer Apple Mail, I would still fix the underlying Exchange connection rather than simply abandoning the app.
For company-managed devices, I would also check with IT before changing mail applications because some organizations enforce specific security or mobile-device-management policies.
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Apple Is Already Working on a Longer-Term Change
Apple says it is working with Microsoft to move Mail, Calendar, Contacts, Notes and Reminders to the Microsoft Graph API in a future macOS 27 update.
That is important because it shows the current EWS situation is transitional.
The long-term direction is not for Apple Mail to remain dependent on the same Exchange Web Services integration indefinitely.
Until that migration reaches affected Macs, however, Exchange administrators may still need to handle the current EWS configuration correctly.
What I Would Not Do
I would not start by resetting the whole Mac.
I would not repeatedly change the Microsoft 365 password unless there is evidence that the password itself is wrong.
I would also avoid manually configuring random IMAP and SMTP servers for a Microsoft 365 business account before testing the normal Exchange setup.
Most importantly, if multiple company Macs stopped syncing at the same time after the October 2026 changes, I would stop treating it as an individual device problem.
That is exactly the kind of situation where the Exchange administrator needs to check the tenant configuration.
Bottom Line
If Apple Mail stopped syncing with Microsoft 365, I would troubleshoot it in this order:
- Confirm the Microsoft 365 account still works in the browser.
- Re-enter the account credentials in Apple Mail.
- Remove the Exchange account and add it again if reauthentication fails.
- If the problem is on macOS and still persists, contact the Exchange administrator.
- Ask the administrator to check the October 2026 EWS requirements and the Apple Internet Accounts allow list.
Microsoft currently confirms that some Microsoft 365 accounts are being disconnected from Apple Mail and recommends reauthentication followed by removing and re-adding Exchange if necessary.
Separately, Apple confirms that some macOS Exchange failures beginning in October 2026 may require an administrator-side EWS change, including allowing Apple Internet Accounts using App ID f8d98a96-0999-43f5-8af3-69971c7bb423.
That is the key thing I would check before wasting time rebuilding the Mac.
Sources
- Microsoft Support — Reconnecting your Microsoft 365 account to Apple Mail
- Apple Support — If you can no longer sign in with a Microsoft Exchange account on macOS
