我使用系统：Debian Testing AMD64 ；新装的系统；
我之前使用 Debian Lenny AMD64 可以安装成功；

< INFO > Continue? [Y|n]
< INFO > Installing package(s): apache2 apache2-mpm-prefork apache2.2-common libapache2-mod-php5 libapache2-mod-auth-mysql php5-cli php5-imap php5-gd php5-mcrypt php5-mysql php5-ldap postfix postfix-pcre awstats mysql-server-5.0 mysql-client-5.0 postfix-ldap slapd ldap-utils postfix-policyd dovecot-imapd dovecot-pop3d amavisd-new libcrypt-openssl-rsa-perl libmail-dkim-perl clamav-freshclam clamav-daemon spamassassin altermime libmail-spf-perl libapache2-mod-wsgi python-mysqldb python-ldap python-jinja2 python-netifaces python-webpy bzip2 acl mailx patch cron tofrodos
Reading package lists... Done
Building dependency tree
Reading state information... Done
apache2 is already the newest version.
apache2 set to manually installed.
apache2-mpm-prefork is already the newest version.
apache2.2-common is already the newest version.
apache2.2-common set to manually installed.
libapache2-mod-php5 is already the newest version.
bzip2 is already the newest version.
acl is already the newest version.
Package mailx is a virtual package provided by:
  mailutils 1:2.1+dfsg1-3
  heirloom-mailx 12.4-1.1+b1
  bsd-mailx 8.1.2-0.20090911cvs-2
You should explicitly select one to install.
E: Package mailx has no installation candidate
< ERROR > Installation failed, please check the terminal output.