Platform: SBS 2008
Problem area: Exchange 2007

Hello there

On observing a certificate expiry waring in the event logs for Exchange, I went ahead and created a new certificate using th ecommand New-ExchangeCertificate and the problem was fixed.

Since then, and I believe it may be related, I have had problem l when using an authenticated SmartHost on the send connector. We are using the authenticated SMTP service with dyn.com.

When activating the service and attempt to send messages, the queue shows a 451 Temporary local problem please try again later. If I configure the SmartHost with the mail server from the ISP, which doesnt require authentication, there is no problem. I have also tested SmartHost using the credentials of the Dyn SMTP service on another a server and there it works fine there.  

I figure there is an authentication issue with certificate verification. The server has a current trusted CA certificate installed. Is it a problem with the binding of Exchange SMTP to this certificate?