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eaicheckzone

Check for EAI mail servers on names in a DNS zone

This project has two python scripts and a mysql database.

Overview

The first script, checkmx.py, reads a top-level-domain DNS zone file looking for names delegated with NS records, and checks to see if the each name has an MX, and writes out the ones that do, with the name and IP address of the MX. It also stores in the database the number of domains with MXes and the number of different MXes.

The second script, testmx.py, takes that list of MXes, connects to each, sends an EHLO command, and checks to see if the response includes the 8BITMIME and SMTPUTF8 options. It also looks for the names of common mail software in the intial banner. It stores the results of its tests in the mysql database.

Prerequisites

  • dnspython

  • pymysql

checkmx.py

Zone files can be quite large, with millions of delegated names, so this script normally samples every Nth name until it's found as many MXes as needed. Since the DNS lookups can be slow, it looks up many at once.

Arguments are:

--sample N Check every Nth name (default 100)

--max N Stop when it's found N MXes

--par N Number of domain checking threads to use (default 100)

--group N Check N domains ate once (default --par)

--res n.n.n.n DNS resolver to use (default is system default)

--timeout N DNS timeout in seconds (default 5)

--tee FILE Write a copy of the domain and MX info into FILE

--v6 Also look for IPv6 addresses in MXes

zone ... List of text or gzipped zone files

testmx.py

Read a list of domains and MXes and check them. It remembers the IP addresses it's checked and will only check each one once. This speeds things up and makes the tests look less like a spambot.

Arguments:

--par N Test N MXes in parallel (default 10)

--timeout N Abandon test if no response in N seconds (default 30)

--addr n.n.n.n Connect from address n.n.n.n (useful on multi-homed machines)

--replace Replace previous results for this TLD in the database

--dbmx Load in previously tested MXes from the database (recommended other than on the first zone file.)

domains ... file(s) in format written by testmx.py, default stdin

Examples

First create the MySQL database using the schema eaimail.sql. Adjust user name and password as needed, and be sure to change them in the two python scripts, too.

For small zones

./checkmx.py --par 1000 --sample 1 --max 1000 --res 8.8.8.8 --tee smallmx zone1.gz zone2.gz | ./testmx.py --par 200 --replace --dbmx

For larger zones

./checkmx.py --par 1000 --sample 100 --max 10000 --tee bigmx zone1.gz zone2.gz | ./testmx.py --par 200 --replace --dbmx

Observations

It's usually faster to use a public resolver like 8.8.8.8 or 9.9.9.9 than to hammer on your local DNS cache.

To get useful results, test from a host that is not in the Spamhaus PBL or other e-mail blacklist. (Most residential broadband networks are added to the PBL by the ISPs.)

Zone files for most ICANN contracted TLDs can be obtained by signing up at the Centralized Zone Data Service at https://czds.icann.org/en

To get zone files for older domains including .com, .org, .info, .asia, and .biz, you have to send an application to the domain's registry to get an FTP password.

License

Copyright 2019-2020 Standcore LLC

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

  1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

  2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

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