Does anyone know if the failure to download the OAB from a workstation not joined to the domain is normal for exchange 2007. Seems to work fine for workstations that are joined to the domain.

It's all about how Outlook tries to connect to the autodiscover service viaDNS. Here'sthe official line from MS, taken from the autodiscover whitepaper at http://technet.microsoft.com/en-us/library/bb332063.aspx: When Outlook 2007 is started on a client that is not domain-connected, it first tries to locate the Autodiscover service by looking up the SCP object in Active Directory. Because the client is unable to contact Active Directory, it tries to locate the Autodiscover service by using Domain Name System (DNS). In this scenario, the client will determine right side of the users e-mail address, that is, contoso.com, and check DNS by using two predefined URLs. For example, if your SMTP domain is contoso.com, Outlook will try the following two URLs to try to connect to the Autodiscover service: https://contoso.com/autodiscover/autodiscover.xml https://autodiscover.contoso.com/autodiscover/autodiscover.xml