Hello!

Has anyone every ran into a problem, when implementing MAPI/HTTP network settings, Outlook 2013 clients are getting log in popups. Even when inserting username and password nothing happens, same popup reappears? Connection to the exchange server is lost after that. No obvious error event's are logged.

When changing connection back to RPC/HTTP Outlook clients work normally.

OWA and EAS continue to work in MAPI/HTTP, only Outlook 2013 dosent.

We have set the Authentication from NTLM to Negotiate and back, but nothing seems to help.

What helps, and only until you close Outlook, is new outlook profile. If you close Outlook the same password prompt comes back.

Have tried changing [HKLM\System\CurrentControlSet\Control\LSA] lmcompatibilitylevel=3 but didnt help.

Any thoughts appreciated.

• Edited by MadOll 17 hours 50 minutes ago

What are your authentication methods for Outlook Anywhere? I suggest setting those to NTLM. You can use 'Get-OutlookAnywhere' in Exchange Management Shell to find this information.

Are you going through a load balancer?  If so which one and can you try routing around the load balancer with a host file?

Hello

please share exchange cu version and client version number.

Please ensure that all available updates are installed for Outlook 2013. Also please verify that MAPI/HTTP is not disabled in the client's registry:https://support.microsoft.com/en-us/kb/2937684