Sendmail is a program which runs on Linux and other Unix-like operating systems, and its function is, as its name suggests, to deliver email. It also receives email. Sendmail is robust, stable, and highly configurable. Sendmail is also one of the oldest programs out there; but it is very complicated. This book aims to tell you what you need to know to get Sendmail to work. It is therefore intended as a book for beginners. Sendmail is difficult to understand, and has many cryptic error messages. After reading through this book, however, you should be able to configure a Sendmail server, and you should be able to understand most of its error messages. This new edition includes more detail on spam (junk mail) filters, including Greylisting, Spamassassin, Sender Address Verification, and ClamAV. It also now includes a chapter on encryption (TLS).