介绍
我最近在 Ubuntu 18.04.3 LTS 虚拟机上安装了postfix 3.3.0 。
为了测试安装，我使用了开箱即用的配置，这意味着我还没有更改任何内容。只有在安装过程中，我才选择Internet site并插入了我的 fqdn example.com。我希望能够在我的域之间发送和传递电子邮件。简单地说，一台服务器可以处理所有邮件。
假设我的域名是example.com.
发送
我可以成功发送电子邮件。我试图sendmail myemailaddress@gmail.com从我的服务器发送电子邮件。在我的 gmail 收件箱中，我可以看到发件人地址是ubuntu@example.com. 发送部分似乎一切正常。
接收
我还可以收到来自我测试过的一些地址的电子邮件。从登录日志可以看出/var/log/mail.log：
Nov 11 21:57:44 mail postfix/smtpd[24956]: connect from f175.i.mail.ru[94.100.178.161]
Nov 11 21:57:44 mail postfix/smtpd[24956]: EB5DA459A4: client=f175.i.mail.ru[94.100.178.161]
Nov 11 21:57:45 mail postfix/cleanup[24959]: EB5DA459A4: message-id=<1573509463.999760544@f175.i.mail.ru>
Nov 11 21:57:45 mail postfix/qmgr[24610]: EB5DA459A4: from=<myemailaddress@list.ru>, size=2917, nrcpt=1 (queue active)
Nov 11 21:57:45 mail postfix/local[24960]: EB5DA459A4: to=<ubuntu@example.com>, relay=local, delay=0.09, delays=0.08/0/0/0.01, dsn=2.0.0, status=sent (delivered to mailbox)
Nov 11 21:57:45 mail postfix/qmgr[24610]: EB5DA459A4: removed
Nov 11 21:57:45 mail postfix/smtpd[24956]: disconnect from f175.i.mail.ru[94.100.178.161] ehlo=2 starttls=1 mail=1 rcpt=1 data=1 quit=1 commands=7
问题是，我无法接收来自 gmail 的邮件。当我从我的 gmail 帐户向 发送电子邮件时ubuntu@example.com，几秒钟后，以下日志会出现在我的服务器中：
Nov 12 08:30:25 mail postfix/smtpd[28230]: connect from mail-wr1-f44.google.com[209.85.221.44]
Nov 12 08:30:25 mail postfix/smtpd[28230]: NOQUEUE: reject: RCPT from mail-wr1-f44.google.com[209.85.221.44]: 454 4.7.1 <ubuntu@example.com>: Relay access denied; from=<myemailaddress@gmail.com> to=<ubuntu@example.com> proto=ESMTP helo=<mail-wr1-f44.google.com>
Nov 12 08:30:25 mail postfix/smtpd[28230]: disconnect from mail-wr1-f44.google.com[209.85.221.44] ehlo=2 starttls=1 mail=1 rcpt=0/1 data=0/1 quit=1 commands=5/7
我想了解的是，这是我这边的配置问题，还是这个错误发生在 gmail 服务器中，然后转发到我的服务器让我知道？
我该如何尝试解决这个问题？
什么是最小、最干净的工作配置，我可以使用它来向所有其他外部邮件服务器发送和传递，就像普通邮件服务器一样可以工作？
编辑
根据要求，这里是/etc/postfix/main.cf：
# 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 $mail_name (Ubuntu)
biff = no
# appending .domain is the MUA's job.
append_dot_mydomain = no
# Uncomment the next line to generate "delayed mail" warnings
#delay_warning_time = 4h
readme_directory = no
# See http://www.postfix.org/COMPATIBILITY_README.html -- default to 2 on
# fresh installs.
compatibility_level = 2
# TLS parameters
smtpd_tls_cert_file=/etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_key_file=/etc/ssl/private/ssl-cert-snakeoil.key
smtpd_use_tls=yes
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache
# See /usr/share/doc/postfix/TLS_README.gz in the postfix-doc package for
# information on enabling SSL in the smtp client.
smtpd_relay_restrictions = permit_mynetworks permit_sasl_authenticated defer_unauth_destination
mydomain = example.com
myhostname = mail.$mydomain
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
myorigin = $mydomain
mydestination = $myhostname, $mydomain, localhost, localhost.localdomain
relayhost =
mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128
mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = all
inet_protocols = all
如您所见，到目前为止，我对默认配置所做的唯一mydomain更改是对、和变量myorigin，如上所示。问题完全一样。myhostnamemydestination
编辑 2
这是/etc/postfix/master.cf文件（我没有编辑它）：
#
# Postfix master process configuration file. For details on the format
# of the file, see the master(5) manual page (command: "man 5 master" or
# on-line: http://www.postfix.org/master.5.html).
#
# Do not forget to execute "postfix reload" after editing this file.
#
# ==========================================================================
# service type private unpriv chroot wakeup maxproc command + args
# (yes) (yes) (no) (never) (100)
# ==========================================================================
smtp inet n - y - - smtpd
#smtp inet n - y - 1 postscreen
#smtpd pass - - y - - smtpd
#dnsblog unix - - y - 0 dnsblog
#tlsproxy unix - - y - 0 tlsproxy
#submission inet n - y - - smtpd
# -o syslog_name=postfix/submission
# -o smtpd_tls_security_level=encrypt
# -o smtpd_sasl_auth_enable=yes
# -o smtpd_tls_auth_only=yes
# -o smtpd_reject_unlisted_recipient=no
# -o smtpd_client_restrictions=$mua_client_restrictions
# -o smtpd_helo_restrictions=$mua_helo_restrictions
# -o smtpd_sender_restrictions=$mua_sender_restrictions
# -o smtpd_recipient_restrictions=
# -o smtpd_relay_restrictions=permit_sasl_authenticated,reject
# -o milter_macro_daemon_name=ORIGINATING
#smtps inet n - y - - smtpd
# -o syslog_name=postfix/smtps
# -o smtpd_tls_wrappermode=yes
# -o smtpd_sasl_auth_enable=yes
# -o smtpd_reject_unlisted_recipient=no
# -o smtpd_client_restrictions=$mua_client_restrictions
# -o smtpd_helo_restrictions=$mua_helo_restrictions
# -o smtpd_sender_restrictions=$mua_sender_restrictions
# -o smtpd_recipient_restrictions=
# -o smtpd_relay_restrictions=permit_sasl_authenticated,reject
# -o milter_macro_daemon_name=ORIGINATING
#628 inet n - y - - qmqpd
pickup unix n - y 60 1 pickup
cleanup unix n - y - 0 cleanup
qmgr unix n - n 300 1 qmgr
#qmgr unix n - n 300 1 oqmgr
tlsmgr unix - - y 1000? 1 tlsmgr
rewrite unix - - y - - trivial-rewrite
bounce unix - - y - 0 bounce
defer unix - - y - 0 bounce
trace unix - - y - 0 bounce
verify unix - - y - 1 verify
flush unix n - y 1000? 0 flush
proxymap unix - - n - - proxymap
proxywrite unix - - n - 1 proxymap
smtp unix - - y - - smtp
relay unix - - y - - smtp
-o syslog_name=postfix/$service_name
# -o smtp_helo_timeout=5 -o smtp_connect_timeout=5
showq unix n - y - - showq
error unix - - y - - error
retry unix - - y - - error
discard unix - - y - - discard
local unix - n n - - local
virtual unix - n n - - virtual
lmtp unix - - y - - lmtp
anvil unix - - y - 1 anvil
scache unix - - y - 1 scache
#
# ====================================================================
# Interfaces to non-Postfix software. Be sure to examine the manual
# pages of the non-Postfix software to find out what options it wants.
#
# Many of the following services use the Postfix pipe(8) delivery
# agent. See the pipe(8) man page for information about ${recipient}
# and other message envelope options.
# ====================================================================
#
# maildrop. See the Postfix MAILDROP_README file for details.
# Also specify in main.cf: maildrop_destination_recipient_limit=1
#
maildrop unix - n n - - pipe
flags=DRhu user=vmail argv=/usr/bin/maildrop -d ${recipient}
#
# ====================================================================
#
# Recent Cyrus versions can use the existing "lmtp" master.cf entry.
#
# Specify in cyrus.conf:
# lmtp cmd="lmtpd -a" listen="localhost:lmtp" proto=tcp4
#
# Specify in main.cf one or more of the following:
# mailbox_transport = lmtp:inet:localhost
# virtual_transport = lmtp:inet:localhost
#
# ====================================================================
#
# Cyrus 2.1.5 (Amos Gouaux)
# Also specify in main.cf: cyrus_destination_recipient_limit=1
#
#cyrus unix - n n - - pipe
# user=cyrus argv=/cyrus/bin/deliver -e -r ${sender} -m ${extension} ${user}
#
# ====================================================================
# Old example of delivery via Cyrus.
#
#old-cyrus unix - n n - - pipe
# flags=R user=cyrus argv=/cyrus/bin/deliver -e -m ${extension} ${user}
#
# ====================================================================
#
# See the Postfix UUCP_README file for configuration details.
#
uucp unix - n n - - pipe
flags=Fqhu user=uucp argv=uux -r -n -z -a$sender - $nexthop!rmail ($recipient)
#
# Other external delivery methods.
#
ifmail unix - n n - - pipe
flags=F user=ftn argv=/usr/lib/ifmail/ifmail -r $nexthop ($recipient)
bsmtp unix - n n - - pipe
flags=Fq. user=bsmtp argv=/usr/lib/bsmtp/bsmtp -t$nexthop -f$sender $recipient
scalemail-backend unix - n n - 2 pipe
flags=R user=scalemail argv=/usr/lib/scalemail/bin/scalemail-store ${nexthop} ${user} ${extension}
mailman unix - n n - - pipe
flags=FR user=list argv=/usr/lib/mailman/bin/postfix-to-mailman.py
${nexthop} ${user}