从昨天开始，我们的 Zimbra 服务器就无法发送外部邮件了。星期五我安装了一些更新（用于 shell shock 和内核更新），重新启动后一切正常。但是从昨天开始，向外部收件人发送邮件就无法正常工作了。内部邮件（不使用中继 MTA）可以正常工作。
由于我没有更改任何设置，因此我使用 swaks 检查了远程服务器（Strato）并且它有效：
swaks -s smtp.strato.de -tls -p 587 -f [email protected] -t [email protected] -a -au [email protected] -ap xxxxxx
/opt/zimbra/conf/relay_password 中列出了与 -au 和 -ap 列出的相同凭据
通过 Zimbra 发送邮件时，我从 /var/log/zimbra.log 获得以下内容：
Oct 2 09:00:10 server postfix/smtp[8144]: 3952465A24A: to=<[email protected]>, relay=smtp.strato.de[81.169.145.133]:587, delay=0.55, delays=0.27/0.01/0.26/0, dsn=4.7.0, status=deferred (SASL authentication failed; cannot authenticate to server smtp.strato.de[81.169.145.133]: bad protocol / cancel)
Zimbra main.cf
mail_owner = postfix
bounce_notice_recipient = postmaster
content_filter = smtp-amavis:[127.0.0.1]:10024
smtp_sasl_security_options = noanonymous
relayhost = smtp.strato.de:587
virtual_alias_expansion_limit = 10000
smtpd_sasl_authenticated_header = no
smtp_helo_name = $myhostname
broken_sasl_auth_clients = yes
minimal_backoff_time = 300s
sender_canonical_maps = proxy:ldap:/opt/zimbra/conf/ldap-scm.cf
always_add_missing_headers = yes
smtpd_tls_key_file = /opt/zimbra/conf/smtpd.key
smtpd_helo_required = yes
virtual_transport = error
sendmail_path = /opt/zimbra/postfix/sbin/sendmail
smtpd_sasl_security_options = noanonymous
smtpd_recipient_restrictions = reject_non_fqdn_recipient, permit_mynetworks, reject_unlisted_recipient, reject_non_fqdn_sender, permit
smtpd_relay_restrictions = permit_sasl_authenticated, permit_mynetworks, reject_unauth_destination
smtpd_reject_unlisted_recipient = no
bounce_queue_lifetime = 5d
smtp_sasl_mechanism_filter =
local_header_rewrite_clients = permit_mynetworks,permit_sasl_authenticated
smtpd_data_restrictions = reject_unauth_pipelining
smtpd_milters =
smtpd_tls_security_level = may
smtpd_sender_restrictions = check_sender_access regexp:/opt/zimbra/postfix/conf/tag_as_originating.re, permit_mynetworks, permit_sasl_authenticated, permit_tls_clientcerts, check_sender_access regexp:/opt/zimbra/postfix/conf/tag_as_foreign.re
lmtp_host_lookup = dns
delay_warning_time = 0h
header_checks =
queue_run_delay = 300s
virtual_mailbox_maps = proxy:ldap:/opt/zimbra/conf/ldap-vmm.cf
notify_classes = resource,software
command_directory = /opt/zimbra/postfix/sbin
smtpd_client_restrictions = reject_unauth_pipelining
smtpd_tls_auth_only = yes
virtual_alias_maps = proxy:ldap:/opt/zimbra/conf/ldap-vam.cf
mailq_path = /opt/zimbra/postfix/sbin/mailq
smtpd_banner = $myhostname ESMTP $mail_name
mynetworks = 127.0.0.0/8 192.168.117.0/24 [::1]/128 [fe80::]/64
lmtp_connection_cache_time_limit = 4s
transport_maps = proxy:ldap:/opt/zimbra/conf/ldap-transport.cf
virtual_alias_domains = proxy:ldap:/opt/zimbra/conf/ldap-vad.cf
smtpd_sasl_auth_enable = yes
smtpd_tls_loglevel = 1
maximal_backoff_time = 4000s
virtual_mailbox_domains = proxy:ldap:/opt/zimbra/conf/ldap-vmd.cf
inet_protocols = ipv4
non_smtpd_milters =
daemon_directory = /opt/zimbra/postfix/libexec
smtp_tls_security_level =
alias_maps = hash:/etc/aliases
setgid_group = postdrop
smtp_cname_overrides_servername = no
mydestination = localhost
smtpd_end_of_data_restrictions =
import_environment =
myhostname = mail.example.com
message_size_limit = 1048576000
recipient_delimiter =
in_flow_delay = 1s
smtpd_sasl_tls_security_options = $smtpd_sasl_security_options
queue_directory = /opt/zimbra/data/postfix/spool
propagate_unmatched_extensions = canonical
manpage_directory = /opt/zimbra/postfix/man
smtp_fallback_relay =
smtpd_tls_cert_file = /opt/zimbra/conf/smtpd.crt
smtp_sasl_password_maps = hash:/opt/zimbra/conf/relay_password
lmtp_connection_cache_destinations =
newaliases_path = /opt/zimbra/postfix/sbin/newaliases
smtp_sasl_auth_enable = yes
mailbox_size_limit = 0
disable_dns_lookups = no
这是 Zimbra 8.04。有什么提示吗？
编辑：发送邮件后，日志级别更高，这是我从 zimbra.log 获得的信息：
Oct 2 09:26:51 server postfix/smtp[21000]: warning: SASL authentication failure: ServerSignature expected in SCRAM-SHA-1 input
答案1
正如其他人指出的那样，您的 SMTP 中继可能已发生一些变化。看起来他们改变了他们宣传的身份验证机制。
我不知道它是否会swaks告诉您其输出中使用了哪种身份验证机制，但您可以尝试指定一个身份验证类型，看看是否能够通过。
digest-md5 的参数为：
swaks -s smtp.strato.de -tls -p 587 -f [email protected] -t [email protected] -a digest-md5 -au [email protected] -ap xxxxxx
查看 swaks手册页对于其他身份验证类型（例如 SCRAM-SHA1）。
在 Zimbra main.cf 中，您可以通过设置以下参数（在您的配置中为空）来指定 auth-type：
smtp_sasl_mechanism_filter = digest-md5
如果这没有帮助，也许你错过了系统上的包。