Now that we've discussed the theory of configuring, installing, and testing a sendmail+IDA system, lets take a few moments to look into things that do happen routinely in the life of a mail administrator.
Remote systems sometimes break. Modems or phone lines fail, DNS definitions are set incorrectly due to human error. Networks go down unexpectedly. In such cases, mail administrators need to know how to react quickly, effectively, and safely to keep mail flowing through alternate routes until the remote systems or service providers can restore normal services.
The rest of this chapter is intended to provide you with the solutions to the most frequently encountered ``electronic mail emergencies''.