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Open Relay Database

ORDB Black List

The Open Relay Database, or ORDB, is a publicly available listing of open relays throughout the world. It is a standard Domain Name System Black List (DNSBL). More information about the ORDB can be found on their web site at http://www.ordb.org/.

Entries in the ORDB are made by the creation of A records in the NS at relays.ordb.org. Lookups are done in a standard prepended reverse dotted IP address format to check a particular IP address for inclusion in the DNSBL. Results IPs that are listed in the DNSBL return an IP address of 127.0.0.2.

The ORDB DNSBL is a very safe and accurate DNSBL in include in most SMTP servers. Only independently confirmed IP addresses operating open relays are listed in the DNSBL. And, with the severe consequences of operating an open relay, no remotely serious or legitimate email operator knowingly configures their SMTP servers to operate as an open relay.

The Cool Rule

Rule Name: ORDB/DNSBL
Lookup Host/Format: relays.ordb.org
NS Record Type: A
Match Operator: equals
Match String: 127.0.0.2
DNR to Use: 2
Check Authenticated: 2
Action: refuse
Action Parameter 01: 550 5.7.1 Your server (%ip [%hi]) is in the %bl block list. See http://ordb.org/lookup/?host=%ip for more details.

Download this rule with full entries in a separate text doccument.

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