Outlook username/password prompt issue

[hellocloud2017]

My environment:
Legacy Exchange 2010 server (hosts legacy public folders)
Exchange 2013 hybrid server
Exchange Online
All users migrated to Exchange Online.
We have SSO enabled with Exchange Online.
Issue :-All migrated users are getting Username/Password Prompt everytime they login in the system. If SSO is enabled, users shouldnt get even a single prompt for credentials.
Any help?

[#2 · Accepted solution]

I think more information is required about your setup to be able to provide some help...as you mention, your users should not be asked for credentials in Outlook...once thing to consider here is that you probably have Same Sign On provided by Azure AD Connect and not Single Sing On.

[#3]

Hi Juan,

Thanks for your reply.

We have SecureAuth as SSO provider for O365.

We have tried below article and made suggsted changes. However, prompt is still coming

http://www.pei.com/2016/07/exchange-authentication-prompts-from-2013-back-to-2007-public-folders/

[#4]

Hi @hellocloud2017 

This is most likely related to those public folders. If the users cancel the prompt can they still access their own mail? I assume you've set up hybrid legacy public folders? If so then the next stop after making sure the Exchange 2010 auth is correct would be checking authentication logs on EX2010 to see what's failing and causing prompt.