If you had a list of the words used to describe sendmail, they'd probably include reliable, flexible, configurable, complex, monolithic, and daunting. But you're not likely to find the word easy. Even seasoned sendmail pros are sometimes frustrated by the intricacies of sendmail's configuration files. With a little determination and the help of a good reference book, like sendmail, Third Edition, you can master this demanding program. But when there's a significant point release, like sendmail V8.13, where do you turn? An excellent companion to our popular sendmail, Third Edition, the sendmail 8.13 Companion provides a timely way to document the improvements in V8.13 in parallel with its release. The book highlights the important changes in the latest update to sendmail, pointing out not just what is handy or nice to have, but what's critical in getting the best behavior from sendmail. This is especially important now that spam is on the rise, and because mobile technology requires roving laptops to use encrypted connections. Not surprisingly, many of the changes and additions to V8.13 have been driven by the ongoing fight against spam. Anyone concerned about spam--and who isn't?--will benefit greatly by upgrading to V8.13 sendmail. Among its many enhancements, V8.13 includes new routines that support the SPF sending site authentication standard (in the Milter library), simultaneous connection control, high connection rate control, and finer tuning of SASL parameters. The additions to the Milter library, alone, make upgrading worthwhile, but sendmail's connection control makes it a no-brainer. The key to understanding them is the sendmail 8.13 Companion. The book is divided into twenty-five chapters that parallel the chapters in the third edition of the sendmail book. For instance, if you're interested in Options configuration (Chapter 24 in sendmail), you'll turn to Chapter 24 in your companion volume to find out what's new in V8.13. For a simple dot release (8.12 to 8.13), V8.13 sendmail has added more features, options, and fundamental changes than any other single dot release has included. If you need to set up or manage sendmail, you'll want this companion volume close at hand. Even if you aren't ready to upgrade to V8.13, you'll find the key to understanding them is the sendmail 8.13 Companion a useful guide to understanding and staying current with the latest changes in sendmail.