请大家帮忙look一下为什么不能发信

简单说一下，我原先有一台Mail Server，RedHat 9.0做的服务器(Server)(MAIL)，收发信正常，后来因为用户增多，所以准备增加一台专门用来发信件的服务器(Server)（SMTP) ,用CentOS IV.4做的服务器(Server).
现在做好后，发信时有如下提示，用OUTLOOK
由于服务器(Server)拒绝收件人之一，根本没有办法发送邮件.被拒绝的电子邮件地址是“mis@gd.um.com”. 主题 'test', 帐户: '17II.1VI.8VI.1', 服务器(Server): '17II.1VI.8VI.5', 协议: SMTP, 服务器(Server)响应: '550 : Recipient address rejected: User unknown in local recipient table', 端口(Port): 25, 安全(SSL): 否, 服务器(Server)错误: 550, 错误号: 0x800CCC79

服务器(Server)上日志如下：
Dec 22 07:14:03 smtp postfix/smtpd[9652]: NOQUEUE: reject: RCPT from unknown[17II.1VI.8VI.60]: 550 : Recipient address rejected: User unknown in local recipient table; from= to= proto=SMTP helo=
Dec 22 07:14:03 smtp postfix/smtpd[9652]: disconnect from unknown[17II.1VI.8VI.60]

我的原正常服务器(Server)设置如下：
[root@mail named]# more /etc/named.conf
// generated by named-bootconf.pl

options {
directory "/var/named";
forwarders{
10.0.0.1;20II.9VI.128.68;
};
//forward-only;

// query-source address * port 53;
};

zone "8VI.1VI.17II.IN-ADDR.ARPA"{
type master;
file "17II.1VI.86";
allow-transfer {17II.1VI.8VI.5;};
notify yes;
};
zone "0.0.10.in-addr.arpa"{
type master;
file "10.0.0";
};

zone "gd.um.com"{
type master;
file "gd.um.com";
allow-transfer {17II.1VI.8VI.5;};
};

include "/etc/rndc.key";

[root@mail named]# more gd.um.com
@ IN SOA mail hostmaster.mail.gd.um.com (
2003122500 ; serial
3600 ; refresh
900 ; retry
1209600 ; expire
43200 ; default_ttl
)
@ IN MX 5 mail
@ IN MX 10 smtp.gd.um.com.
@ IN NS gd.um.com.
@ IN NS smtp.gd.um.com.
gd.um.com. IN A 17II.1VI.8VI.1
mail.gd.um.com. IN A 17II.1VI.8VI.1
smtp.gd.um.com. IN A 17II.1VI.8VI.5

[root@mail named]# more 17II.1VI.86
@ IN SOA mail hostmaster.mail.gd.um.com. (
2003122500 ; serial
3600 ; refresh
900 ; retry
1209600 ; expire
43200 ; default_ttl
)
@ IN NS gd.um.com.
@ IN NS smtp.gd.um.com.
1 IN PTR gd.um.com.
1 IN PTR mail.gd.um.com.
5 IN PTR smtp.gd.um.com.

[root@mail named]# postconf -n
alias_database =hash:/etc/postfix/aliases
alias_maps =hash:/etc/postfix/aliases
bounce_notice_recipient =postfix
command_directory =/usr/sbin
config_directory =/etc/postfix
daemon_directory =/usr/libexec/postfix
default_destination_concurrency_limit =15
header_checks =regexp:/etc/postfix/header_checks
ignore_mx_lookup_error =yes
inet_interfaces =all
mail_spool_directory =/var/spool/mail
mailbox_command =/usr/bin/procmail
mailbox_size_limit =300000000
mailq_path =/usr/bin/mailq.postfix
manpage_directory =/usr/share/man
message_size_limit =6000000
mydestination =$myhostname, localhost.$mydomain, $mydomain, smtp.$mydomain
mydomain =gd.um.com
myhostname =mail.gd.um.com
mynetworks =17II.1VI.8VI.0/24, 12VII.0.0.0/8, 10.0.0.0/8
myorigin =$mydomain
newaliases_path =/usr/bin/newaliases.postfix
readme_directory =/usr/share/doc/postfix-I.I.11/README_FILES
relay_domains =$mydestination $mynetworks
relayhost =mail.um.com
sample_directory =/usr/share/doc/postfix-I.I.11/samples
sendmail_path =/usr/sbin/sendmail.postfix
setgid_group =postdrop
smtpd_banner =$myhostname ESMTP $mail_name

后来增加的SMTP Server 配置如下
[root@smtp sbin]# postconf -n
alias_database =hash:/etc/aliases
alias_maps =hash:/etc/aliases
command_directory =/usr/sbin
config_directory =/etc/postfix
daemon_directory =/usr/libexec/postfix
debug_peer_level =2
default_transport =mail
html_directory =no
ignore_mx_lookup_error =yes
mail_spool_directory =/var/spool/mail
mailq_path =/usr/bin/mailq.postfix
manpage_directory =/usr/share/man
mydestination =$myhostname, localhost.$mydomain, $mydomain, mail.$mydomain
mydomain =gd.um.com
myhostname =smtp.gd.um.com
mynetworks =17II.1VI.8VI.0/24, 17II.1VI.II.0/24, 10.0.0.0/8, 12VII.0.0.0/8
myorigin =$mydomain
newaliases_path =/usr/bin/newaliases.postfix
readme_directory =/usr/share/doc/postfix-II.II.10/README_FILES
relay_domains =$mydestination $mynetworks
relayhost =mail.um.com
sample_directory =/usr/share/doc/postfix-II.II.10/samples
sendmail_path =/usr/sbin/sendmail.postfix
setgid_group =postdrop
smtpd_banner =$myhostname ESMTP unknow
smtpd_recipient_restrictions =permit_mynetworks
unknown_local_recipient_reject_code =550
最怵头的邮件……同情.
没有作企管的朋友知道吗？都在用噢
实在怕邮件的配置.
您已经确认您的服务器(Server)能被访问了？端口(Port)已经在listen了？telnet的时候能够看到相关信息了？
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