空壳邮件服务器主配置文件中哪个参数用于设置空壳邮件服务器收到邮件后转发给哪个主邮件服务器？（）

A.systemctl status dovecot
B.systemctl start dovecot
C.systemctl stop dovecot
D.systemctl enable dovecot

A.yum install dovecot
B.yum install telnet
C.yum install telnet-server
D.yum install postfix