Bug#658878: exim4: does not use other smarthost when one fails to resolve

[Tim Bagot]

Package: exim4
Version: 4.72-6+squeeze2
Severity: normal

We have Exim configured with 2 smarthosts, for redundancy:

dc_eximconfig_configtype='smarthost'
[...]
dc_smarthost='mailhost.uk.bluearc.com:mailhost.us.bluearc.com'
[...]

This morning, unfortunately, the second name in that list stopped
resolving. (It is CNAMEd to something that currently returns NXDOMAIN.)
The failure was noted in mainlog like this:

2012-02-06 09:41:38 1RuL4s-0001wA-0A == timb at bluearc.com R=smarthost defer (-36): host lookup for mailhost.us.bluearc.com did not complete (DNS timeout?)

Surprisingly, Exim seems not to have tried using the other, still working,
smarthost at all (the first listed). No messages were delivered until I
removed the faulty smarthost from the configuration and flushed the queue.
It is clearly undesirable that failure of a backup smarthost should
prevent Exim delivering via a preferred smarthost that has not failed.


-- Package-specific info:
Exim version 4.72 #1 built 12-May-2011 18:50:41
Copyright (c) University of Cambridge, 1995 - 2007
Berkeley DB: Berkeley DB 4.8.30: (April  9, 2010)
Support for: crypteq iconv() IPv6 GnuTLS move_frozen_messages DKIM
Lookups: lsearch wildlsearch nwildlsearch iplsearch cdb dbm dbmnz dnsdb dsearch nis nis0 passwd
Authenticators: cram_md5 plaintext
Routers: accept dnslookup ipliteral manualroute queryprogram redirect
Transports: appendfile/maildir/mailstore autoreply lmtp pipe smtp
Fixed never_users: 0
Size of off_t: 8
GnuTLS compile-time version: 2.8.6
GnuTLS runtime version: 2.8.6
Configuration file is /var/lib/exim4/config.autogenerated

-- System Information:
Debian Release: 6.0.3
  APT prefers stable
  APT policy: (990, 'stable'), (500, 'oldstable'), (500, 'stable'), (50, 'unstable'), (50, 'testing')
Architecture: amd64 (x86_64)

Kernel: Linux 2.6.32-5-amd64 (SMP w/12 CPU cores)
Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash

Versions of packages exim4 depends on:
ii  debconf [debconf-2.0]    1.5.36.1        Debian configuration management sy
ii  exim4-base               4.72-6+squeeze2 support files for all Exim MTA (v4
ii  exim4-daemon-light       4.72-6+squeeze2 lightweight Exim MTA (v4) daemon

exim4 recommends no packages.

exim4 suggests no packages.

-- debconf information:
  exim4/drec: