The SMTP driver will attempt to connect to the remote host immediately through the smtp port as listed in /etc/services. If it cannot be reached, or the connection times out, delivery will be re-attempted at a later time.
Delivery on the Internet requires that routes to the destination host be specified in the route-addr format described in chapter-, rather than as a bang path. smail will therefore transform user%host@gateway, where gateway is reached via host1!host2!host3, into the source-route address <@host2,@host3:user%host@gateway> which will be sent as the message's envelope address to host1. To enable these transformation (along with the built-in BIND driver), you have to edit the entry for the smtp driver in the transports file. A sample transports file is given in Appendix-.