Handle large DNS packets
sendmail's -f flag now overrides environment variables

It more closely matches how the original sendmail -f flag worked.
Recognize 0.0.0.0 as a local address

Fixes a difference between how Linux interprets the IP address 0.0.0.0
and how the *BSD systems handle it.

According to RFC 1122, the IP address 0.0.0.0 should always be treated as
an address for "this host, this network".

Part of qmail's loop-detection logic is determining whether or not a given
IP address "is" the current machine. This patch "teaches" qmail that
0.0.0.0 is always the local machine.

[Description by John M. Simpson <jms1@jms1.net>]
Fix .qmail parsing bug

qmail-local handled incorrectly when the first line of a .qmail file
started with whitespace.

[Description by Ismael Luceno <ismael@iodev.co.uk>]
Remove extern int references to errno and rely on the #include

Fixes compilation against glibc-2.3+.

[Description and fix to error.3 by Ismael Luceno <ismael@iodev.co.uk>]
If $QMAILQUEUE is set, invoke it instead of qmail-queue

This could be used to add a program into the qmail-smtpd->qmail-queue
pipeline that could do filtering, rewrite broken headers, etc.

Allows you to do things like virus scanning and RBL checking before the
message ever goes into the queue. If this other program returns a value
other then zero, the SMTP server treats it as a hard or soft error
(depending on the return value) and refuses to accept the message.

[Description merged from netqmail, original patch, and jms1]
qmail-log.5: Add reference to errors from $QMAILQUEUE script
qmail-queue.8: Add explanation of $QMAILQUEUE
Make qmail-smtpd identify itself as netqmail
FAQ: Point to http://cr.yp.to/qmail/faq.html and http://qmail.org/
qmail.7: Identify installation as netqmail and point to http://qmail.org/
INSTALL: point to http://lifewithqmail.org/lwq.html
netqmail 1.04 leftover changes
dns: When checking CNAME, request only CNAME
SPF implementation for qmail

SPF is something like a DNS based "reverse MX" system to designate
permitted senders for mails depending on the domain name. The goal is to
disallow sender address forgery.

The patch is entirely written using the qmail string and DNS functions, and
thus completely integrated into qmail without external dependencies.

It can check incoming mails inside the SMTP daemon, add Received-SPF lines
and optionally block undesired transfers. The check is performed at the
envelope level.