Hello i have a question about the smart host authentication settings in exchange 2007what does the "externally secured" option does if you select it.Thanks

Essentially, it is like telling your Exchange server it does not have to worry about security, since an outside agent is taking care of it. The Below is taken from: http://technet.microsoft.com/en-us/library/aa997170.aspx Externally Secured Authentication You can select the Externally Secured authentication option if you are sure that the network connection between the servers is trusted. This connection may be an IPsec association or virtual private network. Alternatively, the servers may reside in a trusted physically controlled network. This configuration is useful in the following case: You establish mail flow between an Exchange 2007 transport server and an earlier version of Exchange Server or any other SMTP server. You dont want to use Basic authentication. Exchange connectors that are configured as Externally Secured must use dedicated Send connectors and Receive connectors because all connections to the connectors are assumed to be secure. Therefore, Send connectors that are configured as Externally Secured must use a smart host for routing messages. Also, the IP addresses of the target smart hosts must be configured on the connector. Receive connectors that are configured as Externally Secured must have the RemoteIPRanges set to the IP address range of the sending servers. TLS can also be combined with the Externally Secured authentication option to add session confidentiality. You can do this in the Exchange Management Shell if you set the RequireTLS parameter on the connectors to $True.