When the TLS handshake fails, retry delivery with TLS disabled

This adds support for DH parameters from 1024 to 8192 bits.

After an SMTP connection attempt times out, qmail-remote records
the relevant IP address.  If the same address fails again (after
at least two minutes with no intervening successful connections),
qmail-remote assumes that further attempts will fail for at least
another hour.

...to work around a bug in BIND versions earlier than version 4.9.4

We don't use the code any more but it does no harm.

This patch increases the size of the memory buffer that qmail uses when
querying the system for a list of all local IP addresses. This mailing
list message describes the problem and includes the patch file.

see http://www.mail-archive.com/qmail@id.wustl.edu/msg20935.html

This patch changes qmail-remote to skip over MX servers that greet with
codes 400 to 499 and to bounce mail when any MX server that qmail tries
greets with a code 500 to 599.

see http://www-dt.e-technik.uni-dortmund.de/~ma/qmail/patch-qmail-1.03-rfc2821.diff

UltraDNS started blocking UDP-ANY queries so this is a problem.
This will disable domain canonicalization of the envelope address
of outgoing messages. This is as specified by RFC 1123 section 5.2.2.
However this requirement is obsolete and modern MTAs have disabled it
too.