Microsoft has confirmed that the prompting for credentials is due to having multiple accounts attempting to access Office 365 services at the same time. The prompt for the majority of users is due to Skype for Business attempting to access connected services associated to the secondary account configured in Outlook. To correct this problem, users can follow the steps found in the FAQ’s posted on the Skype for Business service page.

http://www.queensu.ca/its/microsoft-office-365/skype-business/faq

Please contact the IT Support Centre if you require assistance in applying the fix.

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Previous Description (February 23, 2018 13:53):

ITS is investigating login issues when a user has multiple accounts configured within one Outlook profile. The problem only occurs when an additional account is being accessed in which Outlook is requiring the password for the secondary account. Users accessing a shared mailbox will not experience this problem.

If you are experiencing either of the following, please submit a help ticket with the ITSC
• Outlook is requesting a password for an additional account in which entering the password fails to work
• Outlook is displaying “Sorry, another account from your organization is already signed in on this computer.”

Currently, the work around for this problem is to close the password prompt and to access the secondary email account directly in another Outlook profile or to access the email using a Web Browser to access Office 365 email.