一切正常，没有更改 DNS 或电子邮件服务器设置。然后，当某些用户（并非全部）发送电子邮件（某些用户和域名以及 ip 已更改）时，我们收到以下错误。
这仅发生在某些电子邮件用户身上。
De: MAILER-DAEMON [mailto:MAILER-DAEMON] Enviado el: lunes, 25 de junio de 2012 01:49 p.m.
Para: someuser@bizdomain.com
Asunto: Undelivered Mail Returned to Sender
This is the mail system at host mail182-ch112-RR.bigfish.com.
I'm sorry to have to inform you that your message could not be delivered to one or more recipients. It's attached below.
For further assistance, please send mail to postmaster.
If you do so, please include this problem report. You can delete your own text from the attached returned message.
The mail system
<virgilio@sent_to_domain.com>: host
zsca-138961-mail2.customer.somethingbridge.com[156.111.222.16] said:
554-Transaction failed (id=4FE8B30610BE0008), maximum 8 recipients listed
below: 554-Address:virgilio@sent_to_domain.com Server:999.551.11.130
Command:EODT Error:554 5.7.1 Message refused by DNSBL check.
bl.spamcop.net
/ 555.111.2.52 This email has been rejected. The email message was
detected as spam 554 Transaction failed (in reply to end of DATA command)
错误的根源是什么？