我在使用 postfix 时遇到了问题。当我尝试从命令行发送一些邮件时，我收到：
Feb 14 12:44:35 some-server postfix/smtp[1022]: connect to gmail-smtp-in.l.google.com[2a00:1450:4010:c07::1a]:25: Network is unreachable
Feb 14 12:45:05 some-server postfix/smtp[1022]: connect to gmail-smtp-in.l.google.com[64.233.164.27]:25: Connection timed out
Feb 14 12:45:05 some-server postfix/smtp[1022]: connect to alt1.gmail-smtp-in.l.google.com[2404:6800:4008:c07::1a]:25: Network is unreachable
Feb 14 12:45:35 some-server postfix/smtp[1022]: connect to alt1.gmail-smtp-in.l.google.com[64.233.189.27]:25: Connection timed out
Feb 14 12:45:35 some-server postfix/smtp[1022]: connect to alt2.gmail-smtp-in.l.google.com[2404:6800:4008:c01::1b]:25: Network is unreachable
Feb 14 12:45:35 some-server postfix/smtp[1022]: D23CB41F3B: to=<[email protected]>, relay=none, delay=60, delays=0.03/0/60/0, dsn=4.4.1, status=deferred (connect to alt2.gmail-smtp-in.l.google.com[2404:6800:4008:c01::1b]:25: Network is unreachable)
当我尝试 telnet 到 smtp.gmail.com:25 时：
~$ telnet smtp.gmail.com 25
Trying 64.233.164.108...
然后它就挂了。
知道为什么它不起作用吗？我应该检查什么？防火墙 25 端口（也是 465/587）已打开，main.cf 配置：
# See /usr/share/postfix/main.cf.dist for a commented, more complete version
# Debian specific: Specifying a file name will cause the first
# line of that file to be used as the name. The Debian default
# is /etc/mailname.
#myorigin = /etc/mailname
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 = some-server.e24cloud.com
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
myorigin = /etc/mailname
mydestination = some-server.domain, some-server.e24cloud.com, localhost.e24cloud.com, 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
编辑：
ifconfig 和 ufw 设置：
eth0 Link encap:Ethernet HWaddr 52:54:00:9b:81:8a
inet addr:12.34.56.78 Bcast:255.255.248.0 Mask:255.255.248.0
inet6 addr: fe80::5054:ff:fe9b:818a/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:1460047 errors:0 dropped:0 overruns:0 frame:0
TX packets:1482450 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:224872395 (224.8 MB) TX bytes:5739336340 (5.7 GB)
ufw status
Status: active
To Action From
-- ------ ----
Apache ALLOW Anywhere
3306 ALLOW Anywhere
21/tcp ALLOW Anywhere
115/tcp ALLOW Anywhere
14956 ALLOW Anywhere
25/tcp ALLOW Anywhere
587 ALLOW Anywhere
12257/tcp ALLOW Anywhere
80/tcp ALLOW Anywhere
443 ALLOW Anywhere
Apache Full ALLOW Anywhere
Bind9 ALLOW Anywhere
Apache Secure ALLOW Anywhere
OpenSSH ALLOW Anywhere
1022/tcp ALLOW Anywhere
12257 ALLOW Anywhere
25 ALLOW Anywhere
22 ALLOW Anywhere
9418/tcp ALLOW Anywhere
21 (v6) ALLOW Anywhere (v6)
Apache (v6) ALLOW Anywhere (v6)
3306 (v6) ALLOW Anywhere (v6)
21/tcp (v6) ALLOW Anywhere (v6)
115/tcp (v6) ALLOW Anywhere (v6)
14956 (v6) ALLOW Anywhere (v6)
25/tcp (v6) ALLOW Anywhere (v6)
587 (v6) ALLOW Anywhere (v6)
12257/tcp (v6) ALLOW Anywhere (v6)
80/tcp (v6) ALLOW Anywhere (v6)
443 (v6) ALLOW Anywhere (v6)
Apache Full (v6) ALLOW Anywhere (v6)
Bind9 (v6) ALLOW Anywhere (v6)
Apache Secure (v6) ALLOW Anywhere (v6)
OpenSSH (v6) ALLOW Anywhere (v6)
1022/tcp (v6) ALLOW Anywhere (v6)
12257 (v6) ALLOW Anywhere (v6)
25 (v6) ALLOW Anywhere (v6)
22 (v6) ALLOW Anywhere (v6)
9418/tcp (v6) ALLOW Anywhere (v6)