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diff --git a/doc/Qmail/BLURB b/doc/Qmail/BLURB new file mode 100644 index 0000000..48ae4c4 --- /dev/null +++ b/doc/Qmail/BLURB @@ -0,0 +1,222 @@ +Qmail BLURB +=========== + +qmail is a secure, reliable, efficient, simple message transfer agent. +It is meant as a replacement for the entire sendmail-binmail system on +typical Internet-connected UNIX hosts. + +Secure: Security isn't just a goal, but an absolute requirement. Mail +delivery is critical for users; it cannot be turned off, so it must be +completely secure. (This is why I started writing qmail: I was sick of +the security holes in sendmail and other MTAs.) + +Reliable: qmail's straight-paper-path philosophy guarantees that a +message, once accepted into the system, will never be lost. qmail also +supports maildir, a new, super-reliable user mailbox format. Maildirs, +unlike mbox files and mh folders, won't be corrupted if the system +crashes during delivery. Even better, not only can a user safely read +his mail over NFS, but any number of NFS clients can deliver mail to him +at the same time. + +Efficient: On a Pentium under BSD/OS, qmail can easily sustain 200000 +local messages per day---that's separate messages injected and delivered +to mailboxes in a real test! Although remote deliveries are inherently +limited by the slowness of DNS and SMTP, qmail overlaps 20 simultaneous +deliveries by default, so it zooms quickly through mailing lists. (This +is why I finished qmail: I had to get a big mailing list set up.) + +Simple: qmail is vastly smaller than any other Internet MTA. Some +reasons why: (1) Other MTAs have separate forwarding, aliasing, and +mailing list mechanisms. qmail has one simple forwarding mechanism that +lets users handle their own mailing lists. (2) Other MTAs offer a +spectrum of delivery modes, from fast+unsafe to slow+queued. qmail-send +is instantly triggered by new items in the queue, so the qmail system +has just one delivery mode: fast+queued. (3) Other MTAs include, in +effect, a specialized version of inetd that watches the load average. +qmail's design inherently limits the machine load, so qmail-smtpd can +safely run from your system's inetd. + +Replacement for sendmail: qmail supports host and user masquerading, +full host hiding, virtual domains, null clients, list-owner rewriting, +relay control, double-bounce recording, arbitrary RFC 822 address lists, +cross-host mailing list loop detection, per-recipient checkpointing, +downed host backoffs, independent message retry schedules, etc. In +short, it's up to speed on modern MTA features. qmail also includes a +drop-in ``sendmail'' wrapper so that it will be used transparently by +your current UAs. + +Mailing Lists +============= + +Mailing list management is one of qmail's strengths. Notable features: + +* qmail lets each user handle his own mailing lists. The delivery +instructions for user-whatever go into ~user/.qmail-whatever. + +* qmail makes it really easy to set up mailing list owners. If the user +touches ~user/.qmail-whatever-owner, all bounces will come back to him. + +* qmail supports VERPs, which permit completely reliable automated +bounce handling for mailing lists of any size. + +* SPEED---qmail blasts through mailing lists an order of magnitude +faster than sendmail. For example, one message was successfully +delivered to 150 hosts around the world in just 70 seconds, with qmail's +out-of-the-box configuration. + +* qmail automatically prevents mailing list loops, even across hosts. + +* qmail allows inconceivably gigantic mailing lists. No random limits. + +* qmail handles aliasing and forwarding with the same simple mechanism. +For example, Postmaster is controlled by ~alias/.qmail-postmaster. This +means that cross-host loop detection also applies to aliases. + +* qmail supports the ezmlm mailing list manager, which easily and +automatically handles bounces, subscription requests, and archives. + +Features +======== + +Here are some of qmail's features. + +Setup: +* automatic adaptation to your UNIX variant---no configuration needed +* AIX, BSD/OS, FreeBSD, HP/UX, Irix, Linux, OSF/1, SunOS, Solaris, and more +* automatic per-host configuration (config, config-fast) +* quick installation---no big list of decisions to make + +Security: +* clear separation between addresses, files, and programs +* minimization of setuid code (qmail-queue) +* minimization of root code (qmail-start, qmail-lspawn) +* five-way trust partitioning---security in depth +* optional logging of one-way hashes, entire contents, etc. (QUEUE_EXTRA) + +Message construction (qmail-inject): +* RFC 822, RFC 1123 +* full support for address groups +* automatic conversion of old-style address lists to RFC 822 format +* sendmail hook for compatibility with current user agents +* header line length limited only by memory +* host masquerading (control/defaulthost) +* user masquerading ($MAILUSER, $MAILHOST) +* automatic Mail-Followup-To creation ($QMAILMFTFILE) + +SMTP service (qmail-smtpd): +* RFC 821, RFC 1123, RFC 1651, RFC 1652, RFC 1854 +* 8-bit clean +* 931/1413/ident/TAP callback (tcp-env) +* relay control---stop unauthorized relaying by outsiders (control/rcpthosts) +* no interference between relay control and forwarding +* tcpd hook---reject SMTP connections from known abusers +* automatic recognition of local IP addresses +* per-buffer timeouts +* hop counting + +Queue management (qmail-send): +* instant handling of messages added to queue +* parallelism limit (control/concurrencyremote, control/concurrencylocal) +* split queue directory---no slowdown when queue gets big +* quadratic retry schedule---old messages tried less often +* independent message retry schedules +* automatic safe queueing---no loss of mail if system crashes +* automatic per-recipient checkpointing +* automatic queue cleanups (qmail-clean) +* queue viewing (qmail-qread) +* detailed delivery statistics (qmailanalog, available separately) + +Bounces (qmail-send): +* QSBMF bounce messages---both machine-readable and human-readable +* HCMSSC support---language-independent RFC 1893 error codes +* double bounces sent to postmaster + +Routing by domain (qmail-send): +* any number of names for local host (control/locals) +* any number of virtual domains (control/virtualdomains) +* domain wildcards (control/virtualdomains) +* configurable percent hack support (control/percenthack) +* UUCP hook + +SMTP delivery (qmail-remote): +* RFC 821, RFC 974, RFC 1123 +* 8-bit clean +* automatic downed host backoffs +* artificial routing---smarthost, localnet, mailertable (control/smtproutes) +* per-buffer timeouts +* passive SMTP queue---perfect for SLIP/PPP (serialmail, available separately) + +Forwarding and mailing lists (qmail-local): +* address wildcards (.qmail-default, .qmail-foo-default, etc.) +* sendmail .forward compatibility (dot-forward, available separately) +* fast forwarding databases (fastforward, available separately) +* sendmail /etc/aliases compatibility (fastforward/newaliases) +* mailing list owners---automatically divert bounces and vacation messages +* VERPs---automatic recipient identification for mailing list bounces +* Delivered-To---automatic loop prevention, even across hosts +* automatic mailing list management (ezmlm, available separately) + +Local delivery (qmail-local): +* user-controlled address hierarchy---fred controls fred-anything +* mbox delivery +* reliable NFS delivery (maildir) +* user-controlled program delivery: procmail etc. (qmail-command) +* optional new-mail notification (qbiff) +* optional NRUDT return receipts (qreceipt) +* conditional filtering (condredirect, bouncesaying) + +POP3 service (qmail-popup, qmail-pop3d): +* RFC 1939 +* UIDL support +* TOP support +* APOP hook +* modular password checking (checkpassword, available separately) + + +Internals +========= + +qmail's modular, lightweight design and sensible queue management make +it the fastest available message transfer agent. Here's how it stacks up +against the competition in five different speed measurements. + +* Scheduling: I sent a message to 8192 ``trash'' recipients on my home +machine. All the deliveries were done in a mere 78 seconds---a rate of +over 9 million deliveries a day! Compare this to the speed advertised +for Zmailer's scheduling: 1.1 million deliveries a day on a +SparcStation-10/50. (My home machine is a 16MB Pentium-100 under BSD/OS, +with the default qmail configuration. qmail's logs were piped through +accustamp and written to disk as usual.) + +* Local mailing lists: When qmail is delivering a message to a mailbox, +it physically writes the message to disk before it announces success--- +that way, mail doesn't get lost if the power goes out. I tried sending a +message to 1024 local mailboxes on the same disk on my home machine; all +the deliveries were done in 25.5 seconds. That's more than 3.4 million +deliveries a day! Sending 1024 copies to a _single_ mailbox was just as +fast. Compare these figures to Zmailer's advertised rate for throwing +recipients away without even delivering the message---only 0.48 million +per day on the SparcStation. + +* Mailing lists with remote recipients: qmail uses the same delivery +strategy that makes LSOFT's LSMTP so fast for outgoing mailing lists--- +you choose how many parallel SMTP connections you want to run, and qmail +runs exactly that many. Of course, performance varies depending on how +far away your recipients are. The advantage of qmail over other packages +is its smallness: for example, one Linux user is running 60 simultaneous +connections, without swapping, on a machine with just 16MB of memory! + +* Separate local messages: What LSOFT doesn't tell you about LSMTP is +how many _separate_ messages it can handle in a day. Does it get bogged +down as the queue fills up? On my home machine, I disabled qmail's +deliveries and then sent 5000 separate messages to one recipient. The +messages were all safely written to the queue disk in 23 minutes, with +no slowdown as the queue filled up. After I reenabled deliveries, all +the messages were delivered to the recipient's mailbox in under 12 +minutes. End-to-end rate: more than 200000 individual messages a day! + +* Overall performance: What really matters is how well qmail performs +with your mail load. Red Hat Software found one day that their mail hub, +a 48MB Pentium running sendmail 8.7, was running out of steam at 70000 +messages a day. They shifted the load to qmail---on a _smaller_ machine, +a 16MB 486/66---and now they're doing fine. |