The sendmail program can keep the system
administrator up to date about many aspects of mail delivery and
forwarding. It does this by logging its activities using the
syslog(3) facility. Information about things
such as total message volume and site connectivity can help the
administrator make sendmail more efficient.
Information about the SMTP dialog that was used to send the message
can help the administrator solve delivery problems.
In this chapter we cover three important aspects of
sendmail. First, we explain how signals interact
with sendmail and show how signals can be used
to cause sendmail to log additional information.
Second, we show how to use the -X command-line
switch to cause sendmail to record its SMTP
transactions. Finally, we explain the use of the
syslog(3) facility, illustrate several ways to
tune its output, and describe the meaning of that output.