Hi all I have installed Exchange 2013 . I have question about the way Exchange authenticate for external users whose computers are not join domain. My user have domain user account form as : jack.chuong@mydomain.local and use this credential to log on their (joined domain) computer. My user have email account form as : jack.chuong@mydomain.com When I configure MS Outlook for my (joined domain) user's computer, it use NTLM authentication (also known as Integrated Windows authentication) to authenticate with DC , everything works fine. When I configure MS Outlook for my external user's computer (not join domain) manually , I enter Name , Email address : jack.chuong@mydomain.com , and my domain user password. Then it try to connect to autodiscover.mydomain.com and prompt for username/password , at this stage I must enter jack.chuong@mydomain.local or it will fail . Is there anyway to configure Exchange so I can just use jack.chuong@mydomain.com or jack.chuong to authenticate with server for outlook anywhere ? Thanks.

Set the UPN (Logon user account) to jack.chuong@mydomain.com. That is really the best solution. I would recommend that the UPNs match the SMTP addresses ( And SIP Addresses) across your entire org. Makes things much cleaner. Twitter!:

Thank you very much Andy . My problem is solved !