I've recently installed a wildcard certificate on our Exchange 2007 CAS server. After doing this all users have had to change their outlook proxy settings from msstd:servername.domain.com to msstd:*.contoso.com ... I've run the Set-OutlookProvider command to reflect the changes. Still no joy. What the heck am I missing?

There is a technet artical (link below) that addresses your issue. They say if you tried : Set-OutlookProvider -Identity EXPR -CertPrincipalName msstd:*.domain.com Then your only option is to have your outlook users configure their exchange proxy settings. Instructions are included in the link below.http://technet.microsoft.com/en-us/library/cc535023.aspx-Yehoshua24