It is a default application in Mac and saves the information of email account Most of the times, when Mac Outlook 2011 users enter the credentials while making a connection with Office 365. This issue occurs in Mac Outlook because of corruption in the Keychain Access program.
To work around this issue, delete any cached passwords for your account, and also delete any modern authentication tokens from the keychain It stops the authentication process and keeps asking for the password again and again.
to resolve this nuisance To resolve this issue in Outlook 2016 for Mac, install the February 2017 Outlook update (version 15.31.0) from the following Office website: Release notes for Office 2016 for Mac. Please check suggestions in this article. If your Outlook repeatedly prompts for authentication, this issue may occur because of the presence of duplicate tokens in the keychain. Home Outlook Mac keeps prompting for password
