退信内容如下：
Our system has detected an unusual amount of unsolicited
550-5.7.1 mail originating from your IP address. To protect our
550-5.7.1 users from spam, mail sent from your IP address has been
550-5.7.1 rejected. Please visit
550-5.7.1 http://www.google.com/mail/help/bulk_mail.html to review
550 5.7.1 our Bulk Email Senders Guidelines. j7si6878470wah

英文不太好，打开了不太明白些的是什么内容，bulk mail senders 是什么意思呢？

应该是大量邮件发送被当成垃圾邮件被挡了。