Sendmail is the grand-father of all MTAs. It was originally written by Eric Allman while he was at the University of California at Berkeley. The original program, "delivermail", was shipped in 1979 with 4.0 and 4.1 BSD Unix. But delivermail was a very inflexible program. In fact, its configuration was written into it at compile time. As the ARPAnet (the pre-cursor to the modern Internet) was slowly being changed over to TCP (Transmission Control Protocol) from NCP (Network Control Protocol) Eric evolved delivermail into sendmail. His approach was quite liberal but it had to be. For example, during this timeframe UUCP mail often was transmitted with no headers at all, so sendmail had to create them from scratch. This methodology set the standard for MTAs as it required that they be very accepting and make modifications to inbound and outbound mail rather than rejecting it for protocol non-conformance. The first version of sendmail shipped to the world was included with 4.1c BSD which was also the first version of UNIX to include TCP/IP. Since that first release Eric has continued to work on sendmail but he is not the only person to work on sendmail's development.