I don't think I am paving new roads with this tidbit of information but it was somewhat of an obscure find when performing an Exchange 2003 to 2007 upgrade recently. Exchange 2007 Management Console allows many controls when manipulating internal and external URLs for accessing OWA, OAB, EWS, etc. When running the tools at <a href="http://testexchangeconnectivity.com">testexchangeconnectivity.com</a> you may discover an issue with msstd when also using a wildcard certificate. This is because msstd defaults to the subdomain that is used for the External URL of Outlook Anywhere and is generally different from the Autodiscover subdomain. Furthermore it won't match the configure subdomain of the wildcard certificate which is "*". The fix is easy - run the following from the Exchange Management Shell:

Set-OutlookProvider -Identity EXPR -CertPrincipalName msstd:*.yourdomain.com

Here is the authoritative TechNet article from Microsoft:

<a href="http://technet.microsoft.com/en-us/library/cc535023%28EXCHG.80%29.aspx">http://technet.microsoft.com/en-us/library/cc535023%28EXCHG.80%29.aspx</a>