Good link with information on configuring a custom transport link in Postfix. A transport link in a SMTP server is a way to define a communiction/delivery channel with particular settings. Example, you want all e-mails for a particular domain to be sent to a particular server at a particular time.
http://linuxnet.ca/postfix/dedicated_transport.html
In this particular link, the author shows the steps to configure a transport link for sending e-mails to servers/domains with high latency.
