Installing and Administering Internet Services

142 Chapter 4
Installing and Administering sendmail
How sendmail Works
temporary failures, but the attempt to connect to munch fails
permanently, the message will be returned as an error. If the
attempts to connect to bling and wheo result in permanent failures,
but the attempt to connect to munch fails temporarily, the message
will be queued.
• A host cannot deliver a message to another host for which it is a mail
exchanger.
This failure is handled as a normal delivery failure, either by the mail
exchanger host or by the host sending to the mail exchanger.
Default Client-Server Operation
This section describes the operation of sendmail servers and clients.
This section assumes that sendmail is installed as described earlier in
this chapter.
Figure 4-2 shows a sendmail server called mailserv and a sendmail
client called mailclient in the company.com domain. On
mailclient, the SENDMAIL_SERVER_NAME in the
/etc/rc.config.d/mailservs file is set to mailserv.company.com.
user1 is a user on mailclient.