Outlook users are prompted for credentials when they switch from a LAN to a WAN
Article
Applies to:
Microsoft Office Outlook 2007, Outlook 2010, Outlook 2013, Exchange Server 2010 Enterprise, Exchange Server 2010 Standard
Original KB number: 2784787
Symptoms
Assume that domain users connect to Microsoft Exchange Server by using Outlook. The Outlook Anywhere feature is enabled in their Outlook profiles. When the domain users switch from using the LAN to using a WAN, they are prompted for credentials by Outlook.
Cause
This issue occurs when the client authentication method of Outlook Anywhere is set to Basic Authentication on the Exchange server.
When the user switches to another network, Outlook may change the connection type from TCP to HTTPS. If the client authentication method of Outlook Anywhere is set to Basic Authentication, the user is prompted for credentials.
Resolution
To resolve this issue, set the client authentication method of Outlook Anywhere to NTLM Authentication on the Exchange server.
More information
For more information about how to configure Outlook Anywhere on an Exchange server, see:
This module examines how clients connect to Microsoft 365. It also provides instruction on how to configure name resolution and Outlook clients, and how to troubleshoot client connectivity.