1 qmail is a secure, reliable, efficient, simple message transfer agent.

     2 It is meant as a replacement for the entire sendmail-binmail system on

     3 typical Internet-connected UNIX hosts.

     4 

     5 Secure: Security isn't just a goal, but an absolute requirement. Mail

     6 delivery is critical for users; it cannot be turned off, so it must be

     7 completely secure. (This is why I started writing qmail: I was sick of

     8 the security holes in sendmail and other MTAs.)

     9 

    10 Reliable: qmail's straight-paper-path philosophy guarantees that a

    11 message, once accepted into the system, will never be lost. qmail also

    12 supports maildir, a new, super-reliable user mailbox format. Maildirs,

    13 unlike mbox files and mh folders, won't be corrupted if the system

    14 crashes during delivery. Even better, not only can a user safely read

    15 his mail over NFS, but any number of NFS clients can deliver mail to him

    16 at the same time.

    17 

    18 Efficient: On a Pentium under BSD/OS, qmail can easily sustain 200000

    19 local messages per day---that's separate messages injected and delivered

    20 to mailboxes in a real test! Although remote deliveries are inherently

    21 limited by the slowness of DNS and SMTP, qmail overlaps 20 simultaneous

    22 deliveries by default, so it zooms quickly through mailing lists. (This

    23 is why I finished qmail: I had to get a big mailing list set up.)

    24 

    25 Simple: qmail is vastly smaller than any other Internet MTA. Some

    26 reasons why: (1) Other MTAs have separate forwarding, aliasing, and

    27 mailing list mechanisms. qmail has one simple forwarding mechanism that

    28 lets users handle their own mailing lists. (2) Other MTAs offer a

    29 spectrum of delivery modes, from fast+unsafe to slow+queued. qmail-send

    30 is instantly triggered by new items in the queue, so the qmail system

    31 has just one delivery mode: fast+queued. (3) Other MTAs include, in

    32 effect, a specialized version of inetd that watches the load average.

    33 qmail's design inherently limits the machine load, so qmail-smtpd can

    34 safely run from your system's inetd.

    35 

    36 Replacement for sendmail: qmail supports host and user masquerading,

    37 full host hiding, virtual domains, null clients, list-owner rewriting,

    38 relay control, double-bounce recording, arbitrary RFC 822 address lists,

    39 cross-host mailing list loop detection, per-recipient checkpointing,

    40 downed host backoffs, independent message retry schedules, etc. In

    41 short, it's up to speed on modern MTA features. qmail also includes a

    42 drop-in ``sendmail'' wrapper so that it will be used transparently by

    43 your current UAs.