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Gathering DNS Blacklist Filter statistics

Technote (troubleshooting)


Problem

This document explains how to set up and interpret DNSBL statistics in IBM Domino 6.x and later.

Resolving the problem

SMTPExpandDNSBLStats=<n>
This variable, when set to 1, causes the SMTP server to generate host-specific DNS Blacklist Filter statistics, which indicate the total number of hits per DNSBL site, per connecting host's IP address.

If you set SMTPExpandDNSBLStats=0 (or omit it from Notes.INI), the SMTP task maintains statistics that track the total number of connecting hosts that were found on the combined DNSBL of all sites, as well as how many were found on the DNSBL of each configured site.

NOTE: The DNSBL stats will not show up until a positive match has been found on one of your DNS Blacklist sites.

Background: DNS blacklist statistics

The SMTP task maintains statistics that track the total number of connecting hosts that were found on the combined DNSBL of all sites combined, as well as how many were found on the DNSBL of each configured site. Because the statistics are maintained by the SMTP task, they are cumulative for the life of the task only and are lost when the task stops.

You can view the statistics from the Domino Administrator or by using the SHOW STAT SMTP command from the server console. You can further expand the statistics to learn the number of times a given IP address is found on one of the configured DNSBLs. To collect the expanded information, you set the variable SMTPExpandDNSBLStats in the NOTES.INI file on the server. Because of the large numbers generated by the expanded set of statistics, Domino does not record the expanded statistics by default.

With SMTPExpandDNSBLStats = 1:

There are three basic DNSBL stats shown with SMTPExpandDNSBLStats=1:

-- SMTP.DNSBL.<dnsblsite>.Hits
-- SMTP.DNSBL.<dnsblsite>.[X.X.X.X].Hits, where [X.X.X.X] is the ip address of the connecting host.
-- SMTP.DNSBL.TotalHits

SMTP.DNSBL.TotalHits: the number of messages that were rejected because they were found on the blacklist site.
SMTP.DNSBL.<dnsblsite>.Hits: the number of hits for that DNSBL
SMTP.DNSBL.<dnsblsite>.[X.X.X.X].Hits: the number of hits on a DNSBL site for a specific connecting IP

If you are using more than one DNSBL site to query on, then you will see multiple stats for SMTP.DNSBL.<dnsblsite>.Hits and SMTP.DNSBL.<dnsblsite>.[X.X.X.X].Hits for each of the blacklist sites.

With SMTPExpandDNSBLStats = 0:

-- SMTP.DNSBL.<dnsblsite>.Hits
-- SMTP.DNSBL.TotalHits

If you are using more than one DNSBL site to query on, then you will see multiple stats for SMTP.DNSBL.<dnsblsite>.Hits for each of the blacklist sites.

Percentage of blocked mail messages to total attempted
Percentage of messages blocked by the blacklist filtering = SMTP.DNSBL.Hits / (SMTP.MessagesProcessed + SMTP.DNSBL.Hits)

SMTP.MessagesProcessed: The number of messages that were successfully processed for delivery by the SMTP task

NOTE: Domino uses IP version 4 (IPv4) addresses when querying DNS blacklist sites to find out if a connecting host is listed. If the connecting host has an IP version 6 (IPv6) address, Domino skips the DNSBL check for that host.

Document information

More support for: IBM Domino
Mail Server

Software version: 8.0, 8.5, 9.0

Operating system(s): AIX, IBM i, Linux, Solaris, Windows, z/OS

Reference #: 1102611

Modified date: 30 June 2014


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