Yes, you appear to have all the required DLLs. The
RevocationCheckFailed error indicates that the operating system was unable to retrieve a certificate revocation list (CRL) from the server certificate's issuer and perform a check to determine whether the server certificate has been revoked.
To retrieve the CRL, the OS has to be able to connect to the Internet (usually using the HTTP protocol), and if this is not possible, revocation check would fail. Perhaps the CRL is not accessible from your development PC?
There is a built-in utility in Windows called
certutil which you can to run to see what's wrong. First, download the server certificate using the following code:
Smtp client = new Smtp();
client.Settings.SslAcceptAllCertificates = true;
Then, tun the certutil command line utility on the downloaded
certutil -verify -urlfetch cert.der
Please check its output to see whats wrong, and send us a copy (or post it here) if possible.