Whenever we login to outlook 07 we are getting the following error.
There is a problem with the proxy server's security certificate. The name on the security certificate is invalid or does not match the name of the target site exchange. _ _ _ .com.
It's because you're authenticating with TLS (or SSL) and the certificate of the server is not made for the CN of server (the server may have changed his name or changed the whole server). If you trust the server and think there is nobody trying to substitute your server with his own machine (with a bad certificate as they cannot have the same) so you are sure you are connecting to the right server, add an exception to trust the certificate. You can also check with the owner of your server why is this wrong certificate and if they will fix it.
The only real fix here is to change the server certificate to a correct one.