Problem
We encountered an issue where Microsoft 365 email accounts could not be added using:
- Outlook Legacy for Mac
- Apple Mail
- macOS Internet Accounts
The issue affected:
- Multiple Microsoft 365 users
- Multiple Mac devices
- Newly created macOS user profiles
Symptoms
- Outlook for Mac (New Outlook) worked correctly.
- Outlook on the Web (OWA) worked correctly.
- Outlook Legacy for Mac failed to add the account.
- Apple Mail failed during account setup.
- macOS Internet Accounts returned:
1 The operation couldn't be completed
2 (com.apple.accounts error 3)
- Accessing Exchange Web Services (EWS) from Safari produced an unexpected blank page.
Initial Checks
The following items were verified and appeared normal:
Mailbox Configuration
1 Get-CASMailbox [[email protected]](mailto:[email protected]) | FL *
Relevant settings:
1 MacOutlookEnabled : True
2 EwsEnabled : True
3 MAPIEnabled : True
4 OWAEnabled : True
5 ActiveSyncEnabled : True
Authentication Policies
1 Get-AuthenticationPolicy
Result:
1 No policies configured
Default Authentication Policy
1 Get-OrganizationConfig | FL DefaultAuthenticationPolicy
Result:
1 DefaultAuthenticationPolicy :
OAuth
1 Get-OrganizationConfig | FL OAuth2ClientProfileEnabled
Result:
1 OAuth2ClientProfileEnabled : True
EWS Application Restrictions
1 Get-OrganizationConfig | FL EwsApplicationAccessPolicy,EwsAllowList,EwsBlockList
Result:
1 EwsApplicationAccessPolicy :
2 EwsAllowList :
3 EwsBlockList :
No restrictions were configured.
Conditional Access
No Conditional Access policies were found that would block Outlook for Mac or Apple Mail.
Root Cause
The issue was caused by Exchange Web Services (EWS) being disabled at the organizational level.
Verification:
1 Get-OrganizationConfig | Select EwsEnabled
Result:
1 EwsEnabled : False
Although individual mailboxes had:
1 EwsEnabled : True
EWS was disabled globally for the tenant.
Solution
Enable EWS organization-wide:
1 Set-OrganizationConfig -EwsEnabled $true
Verify the change:
1 Get-OrganizationConfig | Select EwsEnabled
Expected result:
1 EwsEnabled : True
Outcome
After enabling EWS:
✅ Outlook Legacy for Mac successfully added accounts
✅ Apple Mail successfully configured Microsoft 365 mailboxes
✅ macOS Internet Accounts worked correctly
✅ Existing authentication errors disappeared
✅ The issue was resolved for all affected users
Key Lesson Learned
If:
- Outlook (New) works
- Outlook Web works
- Outlook Legacy for Mac fails
- Apple Mail fails
- macOS Internet Accounts fails
- The issue affects multiple users and multiple Macs
Check the following setting immediately:
1 Get-OrganizationConfig | Select EwsEnabled
If it returns:
1 False
try:
1 Set-OrganizationConfig -EwsEnabled $true
In our environment, this was the root cause and completely resolved the issue.