UNIX has traditionally delivered mail into a central spool directory,/var/spool/mail. (The original name was /usr/spool/mail; some systemsnow use /var/mail.) There are two basic problems with /var/spool/mail:   * It's slow. On systems with thousands of users, /var/spool/mail has     thousands of entries. A few UNIX systems support fast operations on     large directories, but most don't.   * It's insecure. Writing code that works safely in a world-writable     directory is not easy. See, for example, CERT advisory 95:02.These may not be problems at your site, so you may want to leave yourmailboxes in /var/spool/mail.This file explains several ways that you can configure qmail to useexisting /var/spool/mail delivery tools. Please note that I do not vouchfor the security or reliability of any of those tools.1. What to configureThe qmail system is started from /var/qmail/rc with   qmail-start ./Mailbox splogger qmailThe first argument to qmail-start, ./Mailbox, is the default deliveryinstruction. You can change it to run a program such as binmail orprocmail. (See dot-qmail.0 for the format of delivery instructions.)2. Using procmailYou may already have installed procmail for mail filtering. procmaildelivers to /var/spool/mail by default.To set up qmail to use procmail, simply copy /var/qmail/boot/proc to/var/qmail/rc.Note that procmail must be in your system's boot PATH; if it isn't, youwill have edit /var/qmail/rc to include the full path.3. Using sendmail's delivery agentsendmail uses binmail to deliver to /var/spool/mail. binmail is shippedwith the operating system as /bin/mail or /usr/libexec/mail.local.There is some variation in binmail syntax among systems. The most commoninterfaces are shown in /var/qmail/boot/binm1, /var/qmail/boot/binm2,and /var/qmail/boot/binm3.