This chapter has laid out the most fundamental details of qmail: first how to install a minimal qmail server, then convenient means of controlling the qmail server, and finally the basics of the qmail architecture. The fundamental innovation of qmail is its architecture, and as such the rest of this book is devoted, in one way or another, to examining and exploiting the benefits of that architecture. The next chapter talks about the input end of the qmail mail system.

The next two chapters talk about how to operate the queue—first putting messages into the queue and then controlling how messages exit the queue. In essence, the next two chapters focus on the top and bottom halves, respectively, of the qmail architecture.