Networking :: CentOS Mail Setup - Sendmail Via External SMTP Server

I am setting up a CentOS box as a NAT firewall that needs to also send mail. It needs to send this mail using an outside provider's SMTP. The provider requires SMTP over SSL. None of the machines inside the NAT will ever send mail except via the provider's SMTP nor will they ever receive mail except to local clients via the provider's IMAP servers.

So for the example the machine is TESTMACHINE. There is one internet facing ethernet port connected to a DSL modem via pppoe.

The SMTP it needs to send mail via is mail.host.net which requires SMTP over SSL (port 465) and username/password authentication.

The sendmail documentation is quite confusing on how to get this simple setup operating, so an example showing the appropriate changes to sendmail.mc and other require config files.