当我尝试安装以下软件包时：我正在点击链接 -https://www.howtoforge.com/tutorial/perfect-server-ubuntu-with-nginx-and-ispconfig-3/
apt-get -y install postfix postfix-mysql postfix-doc mysql-client
mysql-server openssl getmail4 rkhunter binutils dovecot-imapd
dovecot-pop3d dovecot-mysql dovecot-sieve dovecot-lmtpd sudo
我收到以下错误：
The following packages have unmet dependencies:
dovecot-lmtpd : Depends: dovecot-core (= 1:2.2.22-1ubuntu2) but 1:2.2.22-1ubuntu2.2 is to be installed
dovecot-mysql : Depends: dovecot-core (= 1:2.2.22-1ubuntu2) but 1:2.2.22-1ubuntu2.2 is to be installed
这是添加到我的源列表中的存储库：
deb http://de.archive.ubuntu.com/ubuntu/ xenial main restricted
deb http://de.archive.ubuntu.com/ubuntu/ xenial-updates main restricted
deb http://de.archive.ubuntu.com/ubuntu/ xenial universe
deb http://de.archive.ubuntu.com/ubuntu/ xenial multiverse
deb http://de.archive.ubuntu.com/ubuntu/ xenial-updates multiverse
deb http://de.archive.ubuntu.com/ubuntu/ xenial-backports main restricted universe multiverse
deb http://security.ubuntu.com/ubuntu xenial-security main restricted
deb http://security.ubuntu.com/ubuntu xenial-security universe
deb http://security.ubuntu.com/ubuntu xenial-security multiverse
它是 ubuntu 16.04。我该如何解决这个问题。