To remove the stored credentials and force Outlook to use your current Windows desktop credentials please do as follows:
Click Start, click on Control Panel, and then click Credential Manager.
Note: If View by (top right) is set to Category, click User Accounts first, and then click Credential Manager.
Ensure that ‘Windows Credentials’ is selected and not ‘Web Credentials’.
Locate a set of credentials that has Outlook in the name – there may be more than one entry.
Click the name to expand the set of credentials, and then click Remove from vault.
Repeat for any other related credentials that you would also like to remove.