If you are using a wildcard SSL certificate for your Exchange services, you may run into some issues when setting up Outlook Anywhere clients. This stems from how the msstd setting defaults. You can set your outlookanywhere external URLs properly, but unless you specify the CertPrincName value, you will get errors because instead of for example mail.domain.com being set, it will default to domain.com.
To fix this, simply run the following Exchange Powershell command:
Set-OutlookProvider EXPR –CertPrincipalName msstd:*.domain.com
Your external outlook anywhere clients should now get the proper configuration from autodiscover
Josef Hanning, PEI