Outlook Anywhere access to Exchange 2013 / Problem with same Proxy URL and different InternalClientAuthenticationMethod and ExternalClientAuthenticationMethod

Hello together,

having the following problem with Exchange 2013 CU2 and Outlook Anywhere access.

We set up the ExternalHostname same like the InternalHostname and use Split DNS.
But the Authentification Methods are different.

ExternalHostname                   : mail.customer.de
InternalHostname                   : mail.customer.de
ExternalClientAuthenticationMethod : Basic
InternalClientAuthenticationMethod : NTLM

Is this a Problem to use the same ExternalHostname than the Internal ?

I have some Issues connecting Outlook Anywhere to Exchange from external. Seems like it is only using NTLM and thats why it wont work.

We have TMG 2010 for reverse Proxy configured to Basic Authentification. I will get a passwort prompt loop or the autoconfiguration vom external is not going through.

When i configure TMG to delegegate the authentification to the exchange Server it is working. Looks like using NTLM then. (internalauthentificationmethod) ?

We do not want to use NTLM on TMG.

Is this a known issue ? How does outlook recognize which authentication to use when having the same proxyaddress ?

i read in that post (http://support.microsoft.com/kb/2754898/de) that generally the outlook connection information from internal can be seen , so how is this about the authentification method ? how can i check what is used actually ?

thanks for feedback,

best,

martin