1.2 Requests for Comments (RFCs)

A complete understanding of sendmail is not possible without at least some exposure to Requests for Comments (RFC) issued by the Internet Engineering Task Force (IETF) at the Network Information Center (NIC). These numbered documents define (among other things) the SMTP and the format of email message headers.

When you see a reference to an RFC in this book, it will appear, for example, as RFC2821. The RFCs of interest to sendmail are listed in the Bibliography at the end of this book.