Postfix can be configured to relay to any other host,
regardless of how DNS MX records are set up. This section discusses the
transport_maps parameter in general.
Later sections and other chapters in the book present specific
configurations that use it.
Conceptually, transport maps override default transport types for
delivery of messages. The
transport_maps parameter points to one or more
transport lookup tables. The following entry sets up /etc/postfix/transport as a transport map
transport_maps = hash:/etc/postfix/transport
The keys in a transport lookup table are either complete email addresses or domains and subdomains. (Email addresses as lookup keys for transport maps require Postfix 2.0 or later.) When a destination address or domain matches a lefthand key it uses the righthand value to determine the delivery method and destination. Example 9-1 lists some possible transport map entries.
Example 9-1. Transport map entries
example.com smtp:[192.168.23.56]:20025 oreilly.com relay:[gateway.oreilly.com] oreillynet.com smtp ora.com maildrop email@example.com error:no mail accepted for kdent
The format of righthand values can differ depending on the
transport type, but generally has the form
nexthop often indicates a host and port
for delivery. Each of the possible portions of the righthand value are
Refers to an entry from master.cf. If you are adding a new transport type, first create an entry for it in ...