http://serverfault.com – Environment is Amazon EC2, running Amazon Linux (Centos-like) with sendmail 8.14.4 and Cyrus sasl 2.1.23. The machine has an elastic IP address that is the target of a domain name, and reverse DNS is setup for it. MX record points at an external server, so the machine does not deal with any incoming internet email, only outgoing. For all outgoing off-node email, I want to use a TLS authenticated connection to smtp.googlemail.com. There are lots of tutorials and articles about this kind of setup (several on this site and its sister sites), as it seems to be a fairly popular way of dealing (HowTos)