「TLS が必要ですが、ホスト alt4.gmail-smtp-in.l.google.com [64.233.186.27] では提供されません。」

TLSを使用したEメール送信は機能しません。動作しません。 tls_policy_fileのコピー（Gmailをセキュリティに変更するとTLSが必要であるというエラーが発生します）：

   cat /etc/postfix/tls_policy
   gmail.com       may

main.cf コピー

alias_database = hash:/etc/aliases
 alias_maps = hash:/etc/aliases
 command_directory = /usr/sbin
 config_directory = /etc/postfix
 daemon_directory = /usr/libexec/postfix
 data_directory = /var/lib/postfix
 debug_peer_level = 2
disable_dns_lookups = no
 html_directory = no
inet_interfaces = all
inet_protocols = ipv4
 mail_owner = postfix
 mailq_path = /usr/bin/mailq.postfix
manpage_directory = /usr/share/man
maximal_backoff_time = 14400s
maximal_queue_lifetime = 1d
milter_default_action = accept
minimal_backoff_time = 3600s
mydestination = $myhostname, localhost.$mydomain, localhost
mydomain = abc.com
mynetworks = 10.5.78.0/24, 127.0.0.0/8
myorigin = $myhostname
newaliases_path = /usr/bin/newaliases.postfix
non_smtpd_milters = $smtpd_milters
queue_directory = /var/spool/postfix
readme_directory = /usr/share/doc/postfix-2.6.6/README_FILES
sample_directory = /usr/share/doc/postfix-2.6.6/samples
sendmail_path = /usr/sbin/sendmail.postfix
setgid_group = postdrop
smtp_pix_workarounds = delay_dotcrlf
smtp_tls_CAfile = /etc/pki/tls/certs/ca-bundle.crt
smtp_tls_policy_maps = hash:/etc/postfix/tls_policy
smtpd_client_restrictions = check_client_access hash:/etc/postfix/access
smtpd_milters = inet:127.0.0.1:8891
smtpd_starttls_timeout = 300s
smtpd_tls_CAfile = /etc/pki/tls/certs/abc-int-cert.crt
smtpd_tls_cert_file = /etc/pki/tls/certs/abc.com.crt
smtpd_tls_key_file = /etc/pki/tls/private/abc.com.key
 smtpd_tls_loglevel = 1
  smtpd_tls_mandatory_ciphers = high
  smtpd_tls_mandatory_exclude_ciphers = aNULL, MD5
 smtpd_tls_mandatory_protocols = !SSLv2, !SSLv3
 smtpd_tls_received_header = yes
smtpd_tls_security_level = may 
transport_maps = hash:/etc/postfix/transport
unknown_local_recipient_reject_code = 550