Chapter 14. Signals, Transactions, and Syslog

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.