本实验在redhat虚拟机中实现：（虚拟机通过桥接方式连接PC）
PC IP:192.168.0.102 网关：192.168.0.1(路由器）DNS:192.168.0.1
Redhat IP:192.168.0.105 网关：192.168.0.1(路由器）DNS:192.168.0.1
PC端安装foxmail邮件客户端测试，访问方式1.以IP形式（较简单，可不用DNS）；2.域名形式
DNS服务器: 192.168.0.105 域名： anyone.com 邮件服务器：mail.anyone.com 192.168.0.105
以IP形式访问
1. 安装postfix
先卸载sendmail
rmp -e sendmail --nodeps
安装postfix
yum -y install postfix
2.修改postfix 配置文件main.cf
more /etc/postfix/main.cf
myhostname = mail.anyone.com
mydomain = anyone.com
myorigin = $myhostname
myorigin = $mydomain
inet_interfaces = all
inet_protocols = all
mydestination = $myhostname, $mydomain, localhost, localhost.$mydomain
3. 安装dovecot
yum -y install dovecot
4.修改dovecot配置文件 /etc/dovecot/dovecot.conf
more /etc/dovecot/dovecot.conf|grep -v ^#|grep -v ^$
protocols = imap pop3 lmtp
listen = *
修改/etc/dovecot/conf.d/10-auth.conf
disable_plaintext_auth = no
修改/etc/dovecot/conf.d/10-mail.conf
mail_location = maildir:~/Maildir
5.添加测试账号user1, user2 ，并分别登录创建目录用以存储用户邮件。
user1$ mkdir ~/Maildir
6.开启postfix 和dovecot
service postfix start
serviece dovecot start
查看日志信息，主要用于排错。
tail -f /var/log/maillog
7.虚拟机上不用修改IP等信息
root@redback ~]# ifconfig -a
eth0 Link encap:Ethernet HWaddr 00:0C:29:5B:BA:16
inet addr:192.168.0.105 Bcast:192.168.0.255 Mask:255.255.255.0
[root@redback ~]# route -n
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.0.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
0.0.0.0 192.168.0.1 0.0.0.0 UG 0 0 0 eth0
[root@redback ~]# cat /etc/resolv.conf
nameserver 192.168.0.1
[root@redback ~]# PC上安装客户端测试：
以域名形式访问：
配置DNS 参考上一篇《Redhat配置BIND》
a.在/etc/named.rfc1912.zones文件中添加区域配置文件
zone "anyone.com" IN {
type master;
file "anyone.com.zone.bak";
allow-update { none; };
};
zone "0.168.192.in-addr.arpa" IN {
type master;
file "0.168.192.zone";
allow-update { none; };
};
b.在/var/named 目录下创建anyone.com.zone.bak、0.168.192.zone区域文件，实现正反解析。
[root@redback named]# more anyone.com.zone.bak
$TTL 600
$ORIGIN anyone.com.
@ IN SOA ns1.anyone.com. admin.anyone.com. (
20180930 ; serial
1H ; refresh
1M ; retry
1W ; expire
10M ) ; minimum
IN NS ns1
IN MX 10 mail
ns1 IN A 192.168.0.105
mail IN A 192.168.0.105
www IN A 192.168.0.105
* IN A 192.168.0.105
[root@redback named]# more 0.168.192.zone
$TTL 600
@ IN SOA ns1.anyone.com. admin.anyone.com. (
20180931 ; serial
1H ; refresh
1M ; retry
1W ; expire
10M ) ; minimum
IN NS ns1.anyone.com.
105 IN PTR ns1.anyone.com.
105 IN PTR www.anyone.com.
105 IN PTR mail.anyone.com.c.修改/etc/resolv.conf修改DNS地址为192.168.0.105，并测试。
[root@redback named]# more /etc/host.conf
#order hosts, dns
[root@redback named]# more /etc/resolv.conf
# Generated by NetworkManager
nameserver 192.168.0.105
[root@redback named]# service named start
Starting named: [ OK ]
[root@redback named]# dig mail.anyone.com
; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.68.rc1.el6_10.1 <<>> mail.anyone.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 42127
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 1, ADDITIONAL: 1
;; QUESTION SECTION:
;mail.anyone.com. IN A
;; ANSWER SECTION:
mail.anyone.com. 600 IN A 192.168.0.105
;; AUTHORITY SECTION:
anyone.com. 600 IN NS ns1.anyone.com.
;; ADDITIONAL SECTION:
ns1.anyone.com. 600 IN A 192.168.0.105
;; Query time: 0 msec
;; SERVER: 192.168.0.105#53(192.168.0.105)
;; WHEN: Tue Oct 2 02:08:23 2018
;; MSG SIZE rcvd: 83
[root@redback named]#d.PC端网络连接手动指定DNS为192.168.0.105，测试后并刷新DNS
D:\>nslookup mail.anyone.com
服务器: ns1.anyone.com
Address: 192.168.0.105
名称: mail.anyone.com
Address: 192.168.0.105
D:\>ipconfig /flushdns
Windows IP 配置
已成功刷新 DNS 解析缓存。
D:\>
e.PC端测试收发邮件。
至此，邮件服务器已搭建完毕，通过桥接方式方便测试，不过不能实现公网访问，如要实现，可以从服务商购买一个域名，
指向本机PC公网地址，路由器端做端口映射指向本机私网地址。鉴于运营商封锁了web服务器80端口，以及工信部备案。
可以购买阿里云、腾讯云部署各种服务。