Nullmailer can not send e-mails via IPv6

Hi

We have a number of IPv6 single stacked servers (i.e. they do not have IPv4 connectivity) running Ubuntu server 12.04 (LTS). It seems that Nullmailer is not able to send e-mails via IPv6. I have tested it on Ubuntu 13.10 and it works (same network, configuration and so on).

The log says:

/var/log# tail mail.err
Dec 10 18:24:36 entropy02 nullmailer[3249]: smtp: Failed: Connect failed
Dec 10 18:24:36 entropy02 nullmailer[1276]: Sending failed: Host or network unreachable
Dec 10 18:24:36 entropy02 nullmailer[3250]: smtp: Failed: Connect failed
Dec 10 18:24:36 entropy02 nullmailer[1276]: Sending failed: Host or network unreachable
Dec 10 18:24:36 entropy02 nullmailer[3251]: smtp: Failed: Connect failed
Dec 10 18:24:36 entropy02 nullmailer[1276]: Sending failed: Host or network unreachable
Dec 10 18:24:36 entropy02 nullmailer[3252]: smtp: Failed: Connect failed
Dec 10 18:24:36 entropy02 nullmailer[1276]: Sending failed: Host or network unreachable
Dec 10 18:24:36 entropy02 nullmailer[3253]: smtp: Failed: Connect failed
Dec 10 18:24:36 entropy02 nullmailer[1276]: Sending failed: Host or network unreachable

/var/log# tail mail.log
Dec 10 18:24:36 entropy02 nullmailer[1276]: Starting delivery: protocol: smtp host: relay.netic.dk file: 1385526724.30499
Dec 10 18:24:36 entropy02 nullmailer[3251]: smtp: Failed: Connect failed
Dec 10 18:24:36 entropy02 nullmailer[1276]: Sending failed: Host or network unreachable
Dec 10 18:24:36 entropy02 nullmailer[1276]: Starting delivery: protocol: smtp host: relay.netic.dk file: 1386528453.10486
Dec 10 18:24:36 entropy02 nullmailer[3252]: smtp: Failed: Connect failed
Dec 10 18:24:36 entropy02 nullmailer[1276]: Sending failed: Host or network unreachable
Dec 10 18:24:36 entropy02 nullmailer[1276]: Starting delivery: protocol: smtp host: relay.netic.dk file: 1386217963.16529
Dec 10 18:24:36 entropy02 nullmailer[3253]: smtp: Failed: Connect failed
Dec 10 18:24:36 entropy02 nullmailer[1276]: Sending failed: Host or network unreachable
Dec 10 18:24:36 entropy02 nullmailer[1276]: Delivery complete, 33 message(s) remain.

# cat /etc/nullmailer/remotes
relay.netic.dk smtp

An e-mail address has been configured in the adminaddr file.

It is not a firewall-issue. When I test with tcpdump no packets are being transmitted from the server to the relay host. As previously stated it works on Ubuntu 13.10 (Version: 1:1.11-2) on the same network with the identical configuration.

Output from apport:
ProblemType: Bug
ApportVersion: 2.0.1-0ubuntu17.6
Architecture: amd64
Date: Tue Dec 10 18:14:26 2013
Dependencies:
 coreutils 8.13-3ubuntu3.2
 debconf 1.5.42ubuntu1
 dpkg 1.16.1.2ubuntu7.2
 gcc-4.6-base 4.6.3-1ubuntu5
 libacl1 2.2.51-5ubuntu1
 libattr1 1:2.4.46-5ubuntu1
 libbz2-1.0 1.0.6-1
 libc-bin 2.15-0ubuntu10.5
 libc6 2.15-0ubuntu10.5
 libgcc1 1:4.6.3-1ubuntu5
 liblzma5 5.1.1alpha+20110809-3
 libselinux1 2.1.0-4.1ubuntu1
 libstdc++6 4.6.3-1ubuntu5
 libtinfo5 5.9-4
 lsb-base 4.0-0ubuntu20.3
 multiarch-support 2.15-0ubuntu10.5
 ncurses-bin 5.9-4
 perl-base 5.14.2-6ubuntu2.3
 sed 4.2.1-9
 tar 1.26-4ubuntu1
 tzdata 2013g-0ubuntu0.12.04
 xz-utils 5.1.1alpha+20110809-3
 zlib1g 1:1.2.3.4.dfsg-3ubuntu4
DistroRelease: Ubuntu 12.04
InstallationMedia: Ubuntu-Server 12.04 LTS "Precise Pangolin" - Release amd64 (20120424.1)
MarkForUpload: True
Package: nullmailer 1:1.05-1
PackageArchitecture: amd64
ProcEnviron:
 SHELL=/bin/bash
 TERM=xterm-color
 LANG=en_US.UTF-8
 LANGUAGE=en_US:en
ProcVersionSignature: Ubuntu 3.2.0-35.55-generic 3.2.34
SourcePackage: nullmailer
Tags: precise
Uname: Linux 3.2.0-35-generic x86_64
UpgradeStatus: No upgrade log present (probably fresh install)

Please let me know if you need any further info.