Installing and Administering Internet Services

154 Chapter 4
Installing and Administering sendmail
Troubleshooting sendmail
This is only a test.
.
sendmail responds with the following information:
[e-mail]... Connecting to local host (local)...
[e-mail]... Executing "/bin/rmail -d myname"
[e-mail]... Sent
sendmail has interfaces to three types of delivery agents. In verbose
mode, sendmail reports its interactions with them as follows:
• Mailers that use SMTP to a remote host over a TCP/IP connection
(IPC mailers):
In verbose mode, sendmail reports the name of the mailer used, each
MX host (if any) to which it tries to connect, and each internet address
it tries for each host. Once a connection succeeds, the SMTP
transaction is reported in detail.
• Mailers that run SMTP (locally) over pipes:
The name of the mailer used and the command line passed to exec()
are reported. Then the SMTP transaction is reported in detail. If the
mailer returns an abnormal error status, that is also reported.
• Mailers that expect envelope information from the sendmail
command line and expect message headers and message body from
standard input:
The name of the mailer used and the command line passed to exec()
are reported. If the mailer returns an abnormal error status, that is
also reported.
Contacting the sendmail Daemon to Verify
Connectivity
It is possible to talk to the sendmail daemon and other SMTP servers
directly with the following command:
telnet host 25
This can be used to determine whether an SMTP server is running on
host. If not, your connection attempt will return “Connection refused.”
Once you establish a connection to the sendmail daemon, you can use
the SMTP VRFY command to determine whether the server can route to
a particular address. For example,