We’ve recently migrated a client to Exchange 2010 from Exchange 2007. Soon after we moved the Autodiscover role and subdomain to the new server quite a few Outlook users reported issues with Outlook Anywhere when out and about with their laptops.

Outlook 2007 would complain in some instances that “Mutual Authentication could not be established”. Other users were continously asked for their password when using Outlook. Outlook Web Access was fine however.

The issue came down to the use of wildcard domains. With the new server we had used a wildcard SSL certificate. Autodiscover was telling Outlook to only accept SSL certs in the name of server.domain.com, however the SSL cert was registered, quite normally for a wildcard SSL, to *.domain.com.

The solution was to manually set the CertPrincipleName attribute in Powershell on the Exchange 2010 box. This seemed to work for us though your mileage may vary.