The public folder couldn’t be found because there is no exchange 2010 public folder server.

After several fits with getting the public folders to work with Exchange 2010 in OWA I have finally solved this one. I was getting MSExchange ADAccess Events 2161 and 2157 in the event viewer. I had never seen the detail of these errors. After setting the event logging level for Validation to Expert I found more detailed information. Attribute: WindowsEmailAddress: Error message: Could not convert property WindowsEmailAddress to type SmtpAddress. Error while converting string *email address* to result type Microsoft.Exchange.Data.SmtpAddress: *email address* is not a valid SMTP address.

I was able to use ADSI Edit and navigated  to Configuration - CN=Configuration, DC=domain, DC=co, CN=Services, CN=Microsoft Exchange, CN=exchange name, CN=Administrative Groups, CN=First Administrative Group, CN=Servers, CN=Server, CN=First Administrative Group, CN=Problematic attribute container.

I went into the properties of this and found mail attribute was the problem. I changed this and and the errors were resolved. Public folders were immediately accessible from OWA 2010.