If you are running Outlook 2016 for Mac while connecting to Office 365 and Outlook constantly prompts you for your login credentials, Microsoft has a workaround for you to try.
Microsoft suggests deleting cached passwords associated with your account as well as modern authentication tokens stored in the Keychain.
Tip: If you are not comfortable making changes to your computer, please consult with an IT professional. Before making changes to your computer, be certain to have a current external backup of all files on your computer.
Follow the steps below to try Microsoft’s workaround for this issue:
Note: The steps below will affect all Office applications that utilize modern authentication tokens.
- Close Outlook 2016 for Mac and all open Office applications.
- Open Keychain Access by using one of the following methods:
- With “Finder” as the selected application, click “Utilities” on the “Go” menu. Double-click “Keychain Access”.
- In “Spotlight Search”, type “Keychain Access” and then double-click “Keychain Access” in the search results.
- In the search box of “Keychain Access”, type “Exchange”.
- In the search results box, select each item to view the Account that’s listed at the top, and then press the Delete key. Repeat this step to delete all the items for your Exchange account.
- In the search box, enter “ADAL”.
- In the search results box, select all items whose type is “MicrosoftOffice15_2_Data:ADAL:<GUID>”, and then press the Delete key.
- In the search box, enter “OFFICE”.
- In the search results box, select the items that are named “Microsoft Office Identities Cache 2” and “Microsoft Office Identities Settings 2”, and then press the Delete key.
- Close Keychain Access.
- Re-launch Outlook 2016 for Mac. You will be prompted to enter your login credentials
If all goes well, you will hopefully no longer receive the constant prompts to re-enter your login credentials.