This chapter covers the input end of the qmail mail system. It focuses on the SMTP protocol and related protocols, and the details of how the
tcpserver, qmail-smtpd, and
qmail-queue programs provide that service.
The following diagram is a part of the overall structure of qmail described in Chapter 1.
The only way of getting email into the on-disk queue in qmail is to use the
qmail-queue program. This is a simple program with a single task: take an email and store it in the on-disk queue.
Any program can use
qmail-queue to inject a message into the queue, provided it can present ...