Hello,

we currently try to setup linked mailboxes to be used with outlook. But neither autodiscover nor manual setup seem to work.
OWA however works fine. The Users are in a domain without any Exchange Server, all Servers are in our old Domain. 

The DNS is set to point to the CAS server, so the Server is found. But when I try to access the xml file I get an 401 error. 
From the Remote Connectivity Tester: 

An HTTP 401 Unauthorized response was received from the remote Unknown server. This is usually the result of an incorrect username or password. If you are attempting to log onto an Office 365 service, ensure you are using your full User Principal Name (UPN). HTTP Response Headers: request-id: 8f584323-24f4-4361-92c5-dc0a925f31a3 Server: Microsoft-IIS/8.0 WWW-Authenticate: Negotiate,NTLM,Basic realm="autodiscover.***.de" X-Powered-By: ASP.NET X-FEServer: MAIL-SERVER Date: Thu, 26 Mar 2015 12:04:59 GMT Content-Length: 0 Elapsed Time: 3308 ms.

Not sure how to solve this. Does the User-Domain need the be prepared and then the config exported with Export-AutodiscoverConfig? Shouldn't be the proper DNS entry enough? 

Hi,

According to your description, I understand that linked mailbox cannot use autodiscover service to connect to Exchange server in Exchange forest.
If I misunderstand your concern, please do not hesitate to let me know.

If we deploy Multiple Forests, we can use Export-AutoDiscoverConfig to updates SCP for an Autodiscover service pointer on the Client Access server in the source forest for the target Exchange forest.
For your reference: https://technet.microsoft.com/en-us/library/aa996849.aspx

For your question, please try to create a DNS record in the resource force, point the URL https://mail.com/autodiscover/autodiscover.xml to the IP address of Exchange CAS server.
Then test from client computer in client forest, make sure the URL is available in IE (the expected result is error code 600).

Besides, I find an similar thread about your question. Please refer to:
https://social.technet.microsoft.com/Forums/office/en-US/778b08e7-37cb-44c8-80a6-d51ebe961da1/multiple-domain-hosting-linked-mailbox-autodiscover?forum=exchange2010

Thanks

Is the SCP Export necessary even if we have the DNS Entry? 

The DNS is working, the Autodiscover request reaches the CAS Server, but the IIS gives a 401 Unauthorized 

Hi,

This issue may be caused by confuse permission.
Please open IIS manager and switch to Site---> Default Web Site ---> OWA, open Authentication to double check Basic Authentication is enabled.

Thanks

Basic Auth is enabled and OWA is also not the problem. Login in OWA works for normal and linked mailboxes. It is just Autodiscover and manual Setup in Outlook that does not work. 

Hi,

Would please take a look at below link and Waterboy550s solution:
https://social.technet.microsoft.com/Forums/office/en-US/778b08e7-37cb-44c8-80a6-d51ebe961da1/multiple-domain-hosting-linked-mailbox-autodiscover?forum=exchange2010

Figured it out. Simply added a SRV record to my ISPs Dns server to point _autodiscover._tcp.anothercompanyz.com to email.companyx.com. On the internal Dns server of anothercompanyz.com added a Host A record to point email.companyx.com to the internal IP address (these networks are linked via VPN).

Thanks

Hi,

Would please take a look at below link and Waterboy550s solution

The SRV Record is not the issue, as I wrote the connection to the CA Server works. It is just that the CAS gives an 401 error when trying to access. 

The Problem is solved now, the problem was that the trust was not working correctly so that the authentication did not work. 

• Marked as answer by Forodrim 19 hours 29 minutes ago