Mail Relaying

Up until now, we've mostly considered Postfix in its role as the end node for email messages. That is, messages that arrive at the Postfix system are, for the most part, delivered to the local system. But it's also common to find Postfix serving as an intermediate node on the path a message follows to its ultimate destination. In this chapter we'll look at some of the configuration options for Postfix as a client in MTA-to-MTA communications.