M365, Outlook password issues in MAC error

Since web sign-in works with the same Microsoft 365 business account, the issue is likely in Outlook for Mac local authentication state or a known Outlook sign-in issue rather than the account password itself.

Try these steps in order:

1. Restart Outlook for Mac A known sign-in issue that caused errors such as CAA2000B and 49dvs was fixed in the service. Restart Outlook to pick up the change.
2. Remove and re-add the account in Outlook for Mac If the account uses Microsoft 365 or Exchange with modern authentication:
   • Open Outlook for Mac
   • Go to Outlook > Settings > Accounts
   • Select Manage to remove and re-add the account
   • Sign in again when prompted
   • Verify Outlook can send and receive mail
3. Reset Keychain permissions if prompts keep returning If Outlook or other Office apps repeatedly ask to sign in, ask for keychain access, or show Authentication Session Expired:
   • Quit all Microsoft 365 for Mac apps
   • If prompted for keychain access, select Always Allow
   • If that does not help, restore keychain permissions by following Apple’s keychain access steps from the Microsoft guidance
4. If Outlook 2016 for Mac is in use, clear duplicate tokens from Keychain This applies specifically to Outlook 2016 for Mac repeated authentication prompts:
   • Quit Outlook and all Office apps
   • Open Keychain Access
   • Search for Exchange and delete items for the Exchange account
   • Search for adal and delete items of type MicrosoftOffice15_2_Data:ADAL:<GUID>
   • Search for office and delete Microsoft Office Identities Cache 2 and Microsoft Office Identities Settings 2
   • Reopen Outlook and authenticate again
   Warning: deleting keychain items affects all Office apps that use modern authentication.
5. If the error is specifically 49dvs or CAA2000B An admin can check whether Microsoft Information Protection API is disabled for user sign-in in Microsoft Entra and set Enabled for users to sign-in to Yes.
6. If support is needed from inside Outlook for Mac Go to Help > Contact Support. If Contact Support fails, reset the Apple Keychain by:
   • Closing Outlook and other Office apps
   • Opening Keychain Access from Spotlight
   • Selecting File > Lock All Keychains
   • Then File > Unlock Keychain “login”

The strongest next step for this scenario is:

• remove and re-add the Microsoft 365 account in Outlook,
• then reset keychain permissions,
• and if the displayed code is 49dvs or CAA2000B, have an admin verify the Microsoft Information Protection API sign-in setting.

• Errors CAA2000B, 4usqa, and 49dvs when trying to sign in to classic Outlook and Outlook for Mac
• Update your password in Outlook for Mac
• Office for Mac repeatedly requests keychain access
• Outlook 2016 for Mac repeatedly prompts for authentication
• Contact support within Outlook for Mac