Postfix安装好后客户端无法连接到发送服务器！

xujiejun520

此为故障现象，无法连接到发送服务器！

此为Postconf -n的显示配置
[root@serverback ~]# postconf -n
alias_database = hash:/etc/aliases
alias_maps = hash:/etc/aliases
broken_sasl_auth_clients = yes
command_directory = /usr/sbin
config_directory = /etc/postfix
daemon_directory = /usr/libexec/postfix
debug_peer_level = 2
default_destination_concurrency_limit = 207419
default_process_limit = 50
html_directory = no
inet_interfaces = localhost
mail_owner = postfix
mailbox_size_limit = 1073741824000000
mailq_path = /usr/bin/mailq.postfix
manpage_directory = /usr/share/man
message_size_limit = 1073741824
mydestination = $myhostname, localhost.$mydomain, localhost,$mydomain  mail.$mydomain,www.$mydomian,ftp.$mydomain
mydomain = ky.com
myhostname = serverback.com
mynetworks = 172.17.18.0/24, 127.0.0.0/8
myorigin = ky.com
newaliases_path = /usr/bin/newaliases.postfix
queue_directory = /var/spool/postfix
readme_directory = /usr/share/doc/postfix-2.3.3/README_FILES
relay_domains = ky.com,$mydestination
sample_directory = /usr/share/doc/postfix-2.3.3/samples
sendmail_path = /usr/sbin/sendmail.postfix
setgid_group = postdrop
smtpd_client_restrictions = permit_sasl_authenticated
smtpd_recipient_restrictions = permit_mynetworks,permit_sasl_authenticated,reject_unauth_destination
smtpd_sasl_auth_enable = yes
smtpd_sasl_local_domain = $myhostname
smtpd_sasl_security_options = noanonymous
unknown_local_recipient_reject_code = 550
此为邮件传送后的Maillog
"/var/log/maillog" 6058L, 756740C
Jun 18 13:49:25 serverback dovecot: pop3-login: Login: user=<user1>, method=PLAIN, rip=172.17.18.202, lip=172.17.18.203
Jun 18 13:49:25 serverback dovecot: POP3(user1): Disconnected: Logged out top=0/0, retr=0/0, del=0/1, size=444
Jun 18 13:53:19 serverback dovecot: pop3-login: Login: user=<user1>, method=PLAIN, rip=172.17.18.202, lip=172.17.18.203
Jun 18 13:53:20 serverback dovecot: POP3(user1): Disconnected: Logged out top=0/0, retr=1/460, del=0/1, size=444
Jun 18 13:53:27 serverback dovecot: pop3-login: Login: user=<user1>, method=PLAIN, rip=172.17.18.202, lip=172.17.18.203
Jun 18 13:53:27 serverback dovecot: POP3(user1): Disconnected: Logged out top=0/0, retr=0/0, del=0/1, size=444
Jun 18 13:58:29 serverback dovecot: pop3-login: Aborted login: user=<user1@ky.com>, method=PLAIN, rip=172.17.18.202, lip=172.17.18.203
Jun 18 13:58:37 serverback dovecot: pop3-login: Aborted login: user=<user1>, method=PLAIN, rip=172.17.18.202, lip=172.17.18.203
Jun 18 13:58:47 serverback dovecot: pop3-login: Aborted login: user=<user1@ky.com>, method=PLAIN, rip=172.17.18.202, lip=172.17.18.203
Jun 18 13:58:47 serverback dovecot: pop3-login: Login: user=<user1>, method=PLAIN, rip=172.17.18.202, lip=172.17.18.203
Jun 18 13:58:47 serverback dovecot: POP3(user1): Disconnected: Logged out top=0/0, retr=0/0, del=0/1, size=444
求高人赐教，原因所在！