Hi All,

for some reason external Outlook clients are configuring themselves with the internal settings from the Autodiscover XML. Specifically, the proxy authentication is being set to NTLM, which causes a password prompt loop.

As far as I can tell, the Autodiscover info is correct:

<Type>EXCH</Type>
 <Server>guid@upn</Server>
 ...
 </Protocol>
 <Protocol>
 <Type>EXPR</Type>
 <Server>external URL</Server>
 ... 
 <AuthPackage>Basic</AuthPackage>
 ...
 </Protocol>
 ...
 <Protocol>
 <Type>EXHTTP</Type>
 <Server>internalURL</Server>
 ...
 <AuthPackage>Ntlm</AuthPackage>
 </Protocol>
 <Protocol>
 <Type>EXHTTP</Type>
 <Server>externalURL</Server>
 ...
 <AuthPackage>Basic</AuthPackage>
 </Protocol>

If I manually change the proxy settings on an external client to Basic everything connects, but on the next Autodiscover it gets reset to NTLM.

Anyone seen this before?
Thx in advance - M.

Are the internalhostname and externalhostname the same for Outlook Anywhere? If so, that is expected.

It will use the internal auth method is they are the same.

Hi M,

Thank you for your question.

I agree with Andys advice.

If internalhostname and externalhostname are different, we could use the following command to check if issue persist:

Set-OutlookProvider EXPR -Server $null

If there are any questions regarding this issue, please be free to let me know. 

Best Regard,

Jim