我用 postfix 2.7.1 和 dovecot 1.2.15 设置了我的邮件服务器，一切似乎都很好，但现在我发现使用 @gmx.net 地址的人无法向我发送电子邮件，而是收到错误消息
Connected to <MYIPADDRESS> but sender was rejected.
Remote host said: 530 5.7.0 Must issue a STARTTLS command first
/var/log/mail.log 显示：
postfix/smtpd[22743]: connected to mailout-de.gmx.net[213.165.64.23]
postfix/smtpd[22743]: disconnect from mailout-de.gmx.net[213.165.64.23]
更详细的日志告诉我：
postfix/smtpd[22743]: match_hostname: mailout-de.gmx.net ~? 127.0.0.0/8
postfix/smtpd[22743]: match_hostaddr: 213.165.64.23 ~? 127.0.0.0/8
postfix/smtpd[22743]: match_hostname: mailout-de.gmx.net ~? [::ffff:127.0.0.0]/104
postfix/smtpd[22743]: match_hostaddr: 213.165.64.23 ~? [::ffff:127.0.0.0]/104
postfix/smtpd[22743]: match_hostname: mailout-de.gmx.net ~? [::1]/128
postfix/smtpd[22743]: match_hostaddr: 213.165.64.23 ~? [::1]/128
postfix/smtpd[22743]: match_list_match: mailout-de.gmx.net: no match
postfix/smtpd[22743]: match_list_match: 213.165.64.23: no match
postfix/smtpd[22743]: auto_clnt_open: …