postfix/メールバージョンの更新

私のpostfixのバージョンを確認するとき

postconf -d | grep mail_version

私が得た結果は次のとおりです。

mail_version = 2.11.0 milter_macro_v = $mail_name $mail_version

しかし、実行すると、apt-get install postfix「postfixはすでに最新バージョンです」というメッセージが返されます。

私のソースリストの内容：

# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.
deb http://ubuntu.mirrors.ovh.net/ftp.ubuntu.com/ubuntu/ trusty main restricted
deb-src http://ubuntu.mirrors.ovh.net/ftp.ubuntu.com/ubuntu/ trusty main restricted

## Major bug fix updates produced after the final release of the
## distribution.
deb http://ubuntu.mirrors.ovh.net/ftp.ubuntu.com/ubuntu/ trusty-updates main restricted
deb-src http://ubuntu.mirrors.ovh.net/ftp.ubuntu.com/ubuntu/ trusty-updates main restricted

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team. Also, please note that software in universe WILL NOT receive any
## review or updates from the Ubuntu security team.
deb http://ubuntu.mirrors.ovh.net/ftp.ubuntu.com/ubuntu/ trusty universe
deb-src http://ubuntu.mirrors.ovh.net/ftp.ubuntu.com/ubuntu/ trusty universe
deb http://ubuntu.mirrors.ovh.net/ftp.ubuntu.com/ubuntu/ trusty-updates universe
deb-src http://ubuntu.mirrors.ovh.net/ftp.ubuntu.com/ubuntu/ trusty-updates universe

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu 
## team, and may not be under a free licence. Please satisfy yourself as to 
## your rights to use the software. Also, please note that software in 
## multiverse WILL NOT receive any review or updates from the Ubuntu
## security team.
deb http://ubuntu.mirrors.ovh.net/ftp.ubuntu.com/ubuntu/ trusty multiverse
deb-src http://ubuntu.mirrors.ovh.net/ftp.ubuntu.com/ubuntu/ trusty multiverse
deb http://ubuntu.mirrors.ovh.net/ftp.ubuntu.com/ubuntu/ trusty-updates multiverse
deb-src http://ubuntu.mirrors.ovh.net/ftp.ubuntu.com/ubuntu/ trusty-updates multiverse

## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
deb http://ubuntu.mirrors.ovh.net/ftp.ubuntu.com/ubuntu/ trusty-backports main restricted universe multiverse
deb-src http://ubuntu.mirrors.ovh.net/ftp.ubuntu.com/ubuntu/ trusty-backports main restricted universe multiverse

deb http://security.ubuntu.com/ubuntu trusty-security main restricted
deb-src http://security.ubuntu.com/ubuntu trusty-security main restricted
deb http://security.ubuntu.com/ubuntu trusty-security universe
deb-src http://security.ubuntu.com/ubuntu trusty-security universe
deb http://security.ubuntu.com/ubuntu trusty-security multiverse
deb-src http://security.ubuntu.com/ubuntu trusty-security multiverse

## Uncomment the following two lines to add software from Canonical's
## 'partner' repository.
## This software is not part of Ubuntu, but is offered by Canonical and the
## respective vendors as a service to Ubuntu users.
# deb http://archive.canonical.com/ubuntu precise partner
# deb-src http://archive.canonical.com/ubuntu precise partner

## Uncomment the following two lines to add software from Ubuntu's
## 'extras' repository.
## This software is not part of Ubuntu, but is offered by third-party
## developers who want to ship their latest software.
# deb http://extras.ubuntu.com/ubuntu precise main
# deb-src http://extras.ubuntu.com/ubuntu precise main

とsource.list.d

chris-lea-node_js-precise.list
chris-lea-node_js-precise.list.distUpgrade
chris-lea-node_js-precise.list.save
official-package-repositories.list
ondrej-apache2-precise.list
ondrej-apache2-precise.list.distUpgrade
ondrej-apache2-precise.list.save
ondrej-php-precise.list
ondrej-php-precise.list.distUpgrade
ondrej-php-precise.list.save
ondrej-php-trusty.list
sources.list.save
webupd8team-java-precise.list
webupd8team-java-precise.list.distUpgrade
webupd8team-java-precise.list.save
.swp   

私のサフィックスを最新バージョン3.3.0に更新したいと思います。