Unfortunately, delivermail was not flexible enough to handle the changes in
mail-routing requirements that actually occurred. Perhaps its greatest weakness was
that its configuration was compiled in.
In 1980, ARPAnet began converting from Network Control Protocol (NCP) to
Transmission Control Protocol (TCP). This change increased the number of possible
hosts from 256 to more than 1 billion. Another change converted from a ???flat???
hostname space (such as MIT-XX) into a hierarchical namespace (such as
XX.MIT.EDU). Prior to these changes, mail was transported using the File Transfer
Protocol (FTP). Afterward, a new protocol was developed for transporting mail,
called Simple Mail Transfer Protocol (SMTP). These developments were not instantaneous.
Some networks continued to run NCP years after most others switched to
TCP. And SMTP underwent many revisions before finally settling into its present
form.
Responding to these and other changes, Eric evolved delivermail into sendmail. To
ensure that messages transferred between networks would obey the conventions
required by those networks, Eric took a ???liberal??? approach??”modifying address
This is the Title of the Book, eMatter Edition
Copyright ?© 2007 O??™Reilly & Associates, Inc. All rights reserved.
Preface | xvii
information to conform rather than rejecting it. At the time, for example, UUCP mail
often had no headers, so sendmail had to create them from scratch.
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