To help block spam, the LPL mail server filters incoming connections by consulting the worldwide Spamhaus and Barracuda lists of known spammers. Incoming connections are rejected from any system listed in the Spamhaus or Barracuda databases.
The sender then receives one of the following error messages:
Rejected: ip-address-of-sending-mail-server listed at sbl-xbl.spamhaus.org
Rejected: ip-address-of-sending-mail-server listed at b.barracudacentral.org
Legitimate senders who receive such a message should send an email to sys (LPL Systems)
(using another email account/ISP, like gmail), specifying the from-address that cannot send. LPL Systems staff will help diagnose and correct the problem.