Chapter 2: Getting Email Into the Queue

Chapter 2 does a superb job describing how email finds its way into the qmail queue, whether via local or remote injection, and introduces various tools to summarize, examine, and modify the queue.

Under "qmail-smtpd and the QMAILQUEUE Patch" on Page 30, the author introduces qmail-smtpd, the component of qmail that handles incoming SMTP connections — that is, qmail's SMTP "server", though that component actually handles only one SMTP connection at a time, making it simpler and thus easier to validate (and, in some cases, easier to modify).

Here is where the reader starts learning about deciding whether to accept or reject incoming email, how to allow selective relaying (submission of email, via a qmail SMTP server, to the rest of the Internet, but not promiscuously as an "open relay"), and how to filter (modify) incoming email.

Also introduced are Quick Mail Transfer Protocol (QMTP) and Old-Fashioned Mail Injection Protocol (OFMIP).

Under "POP-before-SMTP" on Page 33, the paragraph beginning "This requires a little explanation" should probably specify that qmail-pop3d is run as the user, not root, in conformance with qmail's security-conscious architecture.

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Copyright (C) 2007 James Craig Burley, Software Craftsperson
Last modified on 2007-07-09.