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反向 DNS 与 SMTP 横幅不匹配

tag-icon • tag-icon dns postfix hostname smtp
反向 DNS 与 SMTP 横幅不匹配

我在我的 Ubuntu 16.04 服务器 (DigitalOcean) 上安装了 Postfix，对于我的网站：example.com，我添加了一个 A 记录 mail.example.com 和一个由 mail.example.com 处理的 example.com 的 MX 记录

它正在运行，但是当我检查我的 mail.example.com wu-ith MXToolBox 时，我收到 1 个警告

Result  
SMTP Banner Check   Reverse DNS does not match SMTP Banner

这是 /etc/postfix/main.cf

/etc/postfix/main.cf

smtpd_banner = $myhostname ESMTP $mail_name (Ubuntu)
biff = no

# appending .domain is the MUA's job.
append_dot_mydomain = no

# Uncomment the next line to generate "delayed mail" warnings
#delay_warning_time = 4h

readme_directory = no

# TLS parameters
smtpd_tls_cert_file=/etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_key_file=/etc/ssl/private/ssl-cert-snakeoil.key
smtpd_use_tls=yes
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache

# See /usr/share/doc/postfix/TLS_README.gz in the postfix-doc package for
# information on enabling SSL in the smtp client.

smtpd_relay_restrictions = permit_mynetworks permit_sasl_authenticated defer_unauth_destination
myhostname = example.com
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
myorigin = /etc/mailname
mydestination = $myhostname, example.com, example, localhost.localdomain, localhost
relayhost = 
mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128
mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = all
inet_protocols = all
home_mailbox = Maildir/
virtual_alias_maps = hash:/etc/postfix/virtual

smtpd_client_restrictions = permit_mynetworks permit_sasl_authenticated reject_unauth_destination reject_rbl_client zen.spamhaus.org reject_rbl_client bl.spamcop.net reject_rbl_client cbl.abuseat.org reject_unknown_client permit

policyd-spf_time_limit = 3600

smtpd_recipient_restrictions =
    reject_unauth_destination,
    check_policy_service unix:private/policyd-spf

# Milter configuration
# OpenDKIM
milter_default_action = accept
# Postfix ≥ 2.6 milter_protocol = 6, Postfix ≤ 2.5 milter_protocol = 2
milter_protocol = 6
smtpd_milters = local:/opendkim/opendkim.sock
non_smtpd_milters = local:/opendkim/opendkim.sock

答案1

错误消息非常直接。横幅与反向 DNS 记录不匹配。您必须向托管服务提供商更新反向记录，或者更新横幅以匹配现有的反向记录。

当客户端连接时，横幅是邮件服务器发送的第一行：

[~]$ nc localhost 25
220 example.com ESMTP Postfix (Debian/GNU)

它由配置行给出

smtpd_banner = $myhostname ESMTP $mail_name (Ubuntu)

$myhostname被主机配置的主机名替换，并被$mail_name正在使用的 MTA 替换。但是您不必使用变量：

smtpd_banner = example.com ESMTP Postfix (Ubuntu)

将工作。

要实际更改反向 DNS，您必须咨询提供商帮助台。对于 DO，这篇帮助文章可能会有帮助。

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