我已经在 CentOS 7 上安装了 Postfix 和 Dovecot。当我尝试从 Outlook 等服务发送/接收电子邮件时，一切运行正常。
但是，当我从 Gmail 帐户向服务器上的电子邮件发送电子邮件时，出现了问题。邮件从未到达我的服务器，而是被送回，这就是消息中提到的原因：
Technical details of temporary failure:
Google tried to deliver your message, but it was rejected by the server for the recipient domain xxxxxxxx.com by xxxxxxxx.com. [xx.zz.186.133].
The error that the other server returned was:
454 4.7.0 TLS not available due to local problem
这是我的main.cf文件：http://pastebin.com/3Di4PYxt
以下是文件夹中的文件/etc/postfix：
access header_checks.inbound.db ldap transport
canonical header_checks.internal main.cf transport.db
generic header_checks.internal.db master.cf virtual
header_checks header_checks.submission relocated
header_checks.inbound header_checks.submission.db ssl
我在 /etc/postfix/ssl 中有这些文件：
server.crt server.csr server.key server.key.secure
我按照本教程安装了邮件服务器：http://www.krizna.com/centos/setup-mail-server-centos-7/
注：我见过这问题，但没有帮助。
答案1
最后我设法通过以下链接解决了该问题：https://workaround.org/ispmail/squeeze/ssl-certificates
必须运行这些命令（以 root 身份）：
mkdir /etc/ssl/private/
openssl req -new -x509 -days 3650 -nodes -out /etc/ssl/certs/dovecot.pem -keyout /etc/ssl/private/dovecot.pem
chmod o= /etc/ssl/private/dovecot.pem
openssl req -new -x509 -days 3650 -nodes -out /etc/ssl/certs/postfix.pem -keyout /etc/ssl/private/postfix.pem
chmod o= /etc/ssl/private/postfix.pem
postconf -e smtpd_tls_cert_file=/etc/ssl/certs/postfix.pem
postconf -e smtpd_tls_key_file=/etc/ssl/private/postfix.pem
service dovecot restart
service postfix restart