This second edition of sendmail covers sendmail Version 8.8 from Berkeley and the standard versions available on most systems. It is far and away the most comprehensive book ever written on sendmail, the program that acts like a traffic cop in routing and delivering mail on Unix-based networks. Although sendmail is used on almost every Unix system, it's one of the last great uncharted territories--and most difficult utilities to learn--in Unix system administration.This book provides a complete sendmail tutorial, plus extensive reference material on every aspect of the program. What's more, it's authoritative, having been coauthored by Eric Allman, the developer of sendmail. In addition to Version 8.8, it covers earlier versions available on many systems, such as those found on Sun workstations. Part One is a tutorial on understanding sendmail; Part Two covers the building, installation, and m4 configuration of sendmail; Part Three covers practical issues in sendmail administration; Part Four is a comprehensive reference section; and Part Five consists of appendixes and a bibliography.In this second edition an expanded tutorial demonstrates hub's cf file and nullclient.mc. Other topics include the #error delivery agent, sendmail's exit values, MIME headers, and how to set up and use the user database, mailertable, and smrsh. Solution-oriented examples throughout the book help you solve your own sendmail problems. Plus, this edition is cross-referenced with section numbers.