This morning one of the Real-time Blackhole Lists (“RBL”) we use to help filter inbound E-mail for SPAM was taken offline. The specific RBL was blackhole.securitysage.com. Apparently this domain name expired and was not renewed. Our gateway server than started to reject some inbound mail because it was unable to reach this RBL.
We have since removed this RBL from our gateway server’s configuration (as of 11:17 AM PDT).
If someone attempted to send you an E-mail this morning, and received the following bounced message, then they should resend the message.
554 Service unavailable; Client host [somehost.somedomain.tld] blocked using blackhole.securitysage.com;