SUMMARY

This article outlines how to integrate your own Reverse DNS Black List (RBL) with MailEnable.

OVERVIEW

MailEnable allows for two types of RBL lookups; these are called Zone lookups and Host lookups. As such, MailEnable performs two very different types of lookups depend on whether the DNS blacklist provider entry is defined as a Zone lookup or a Host lookup.

Host Lookup
A Host lookup is when a DNS server (as defined as the Name Server value in the MailEnable Administration Program) is used to check for the existence of the relevant IP address where the mail is coming from. The Sender's IP Address is converted into reverse byte order in following format: p4.p3.p2.p1.in-addr.arpa. (where IP address is p1.p2.p3.p4) If a PTR record is returned from the DNS server for the address, then the address will be blocked.

Zone Lookup
A Zone lookup relies on using the DNS hosts as defined for the SMTP Connector properties. These servers will in turn be queried for PTR records within the namespace defined as the "Zone" value in the MailEnable Administration Program.

Assuming the Zone name is "multihop.dsbl.org.", then the following PTR lookup would occur:

p4.p3.p2.p1.multihop.dsbl.org. (where IP address is p1.p2.p3.p4)

DETAIL

Configuring DNS and DNS Zones is dependant on a sound understanding of DNS principles and specific to the DNS product that is being used. For more information on configuring DNS, refer to the vendor provided documentation. 

MORE INFORMATION

Please also see the following article in relation to configuring Reverse DNS Blacklists:http://www.mailenable.com/kb/content/article.asp?ID=ME020162