Hello, I have a strange issue and was hoping someone could help.

I'm running Exchange 2013 with 3 CAS servers, 1 is used for a BES server and therefore isn't in load balancing. The other two are externally facing so people can access their emails from anywhere.

Now when people are connecting mostly things are fine but very rarely proxy authentication is changing from Basic to NTLM causing constant prompts for logon details. If on powershell I check Get-OutlookAnywhere, on the two external CAS servers both the internal and external authentication is set to Basic. On the BES server CAS, external is set to basic and internal NTLM (also IIS auth is set to NTLM here whereas it's basic on the other two) which I believe has to be like this for BESx.

Is there somewhere else I should be checking to see where the proxy is being changed or does it seem like external clients are hitting the BES CAS? Unfortunately, I cant see anywhere on 2013 OWA that tells me which CAS server is being hit...

Thanks in advance :)

Hi,

Anyway, let s run Test E-mail AutoConfiguration or ExRCA to confirm which CAS servers autodiscover is used by the problematic clients.

ExRCA: https://www.testexchangeconnectivity.com/

Thanks,
Angela Shi

Hi,

Anyway, let s run Test E-mail AutoConfiguration or ExRCA to confirm which CAS servers autodiscover is used by the problematic clients.

ExRCA: https://www.testexchangeconnectivity.com/

Thanks,
Angela Shi

• Marked as answer by Simon_WuMicrosoft contingent staff, Moderator Saturday, October 05, 2013 6:10 PM
• Unmarked as answer by Ben GT 2 hours 31 minutes ago

Test Exchange connectivity was fine everytime, pulled back no issues. Seems the problem was the BES server, although not in NLB, CAS requests are being passed to it and then it's passing back NTLM to Outlook (set as internal auth method as per instructions from RIM). I have changed the internal auth method on the BES server to basic and it has had no repercussions on BlackBerry users at all and Outlook has stopped picking up NTLM :)

• Marked as answer by Ben GT 2 hours 29 minutes ago