We have an Exchange 2010 sp2 environment hosted in a domain company1.com and have 4 additional smtp namespaces company2, company3, company4 and company5. Activesynch works properly when manually adding connection details on smartphones but fails when attempting to use Autodiscovery.
We are using a SAN certificate and I've created SRV records for autodiscover records for all the required namespaces.
I did have a redirect on the Autodiscover site in IIS on my edge server and I've cleared that. I also tried using the "\" parameter on the basic authentication setting for that site.
I've ran the Remote Connectivity Analyzer and it comes back clean with the exception of this warning;
Analyzing the certificate chains for compatibility problems with versions of Windows.
Potential compatibility problems were identified with some versions of Windows.
The Microsoft Connectivity Analyzer can only validate the certificate chain using the Root Certificate Update functionality from Windows Update. Your certificate may not be trusted on Windows if the "Update Root Certificates" feature isn't enabled.
Elapsed Time: 5 ms.
Everything else looks correct I'm not sure if I'm missing something in the configuration. I've read some resolutions that mention adding the UPN but I tried that and once I added the additional domain I wasn't able to choose it from the drop down on the user account.