An SMTP connector can be used to connect computers running
Exchange 2000 Server; computers running earlier versions of
Exchange; other SMTP-compatible messaging systems, such as the UNIX
sendmail daemon; or SMTP hosts on the Internet. Although a Routing
Group connector is preferred, an SMTP connector can also be used to
connect routing groups within native-mode or mixed-mode Exchange
An SMTP connector is analogous to Internet Mail Service, which
is found in previous versions of Exchange. Although Routing Group
connectors are easier to configure, an SMTP connector offers the
following capabilities that are not available with a Routing Group
The SMTP connector uses a smart host or mail exchanger records
in DNS to route messages to the next server
(although it does relay link state
information when configured between routing groups in
the same Exchange organization). If you designate a smart host,
Exchange transmits information only to the smart host instead of
repeatedly contacting the domain until a connection is made. This
can be helpful when you are sending messages over the Internet, for
example, and the remote domain can be reached infrequently or only
during certain times. The smart host makes the remote connection.
If you do not designate a smart host, a DNS lookup is made for
every address to which the SMTP connector sends mail.
The SMTP connector can be used to connect two independent
Exchange organizations (Active Directory forests) in order to
connect address spaces. It cannot be used to connect routing groups
in two independent organizations.
The SMTP connector allows custom authentication, and encryption
can be enabled for the connection.