NAME

Net::ValidMX - PERL Module to use DNS and/or regular expressions to verify if an email address could be valid.

SYNOPSIS

Net::ValidMX - I wanted the ability to use DNS to verify if an email address COULD be valid by checking for valid MX records. This could be used for sender verification for emails with a program such as MIMEDefang or for websites to verify email addresses prior to registering users and/or sending a confirmation email.

PRE-REQUISITE MODULES

Net::DNS v0.53 or greater. Test::More.

INSTALLATION

To install this package, uncompress the distribution, change to the directory where the files are present and type: 

            perl Makefile.PL
            make
            make test
            make install

USE

To use the module in your programs you will use the line:

use Net::ValidMX;

check_valid_mx
To check if an email address could be valid by checking the DNS, call the function check_valid_mx with a single email address as the only

argument

($rv, $reason) = &Net::validMX::check_valid_mx('kevin.mcgrail@thoughtworthy.com');

check_valid_mx will return a true/false integer as the first value and a descriptive text message as warranted.

NOTE: In the event of a DNS resolution problem, we do NOT return a failure. We return a success to prevent DNS outages and delays from producing too many false positives.

check_email_validity
To check if an email address is formatted correctly, call the function check_email_validity with a single email address as the only argument:

$rv = &Net::validMX::check_valid_mx('kevin.mcgrail@thoughtworthy.com');

check_email_validity will return a true/false integer where > 0 indicates that the email address looks valid.

check_email_and_mx
To check if an email address is formatted correctly, sanitize the email address some common end-user errors(*) and run check_valid_mx all from a single function, use the function check_email_and_mx with a single email address as the only argument:

($rv, $reason, $sanitized_email) = &Net::validMX::check_valid_mx('kevin.mcgrail@thoughtworthy.com');

check_email_and_mx will return a true/false integer where > 0 indicates that the email address looks valid, a descriptive text message as warranted, and a sanitized version of the email address argument .

(*) Common end-user errors that are fixed:

All spaces are stripped. Many users seem to enter things like Bob and Carol @ a big isp.com.
Emails ending in @aol. or @aol

EXAMPLE
The distribution contains an example program to demonstrate working functionality as well to utilize as a command line interface to query one or more email addresses.

Run the program with the space-seperated email addresses to test as your

arguments

perl example/check_email_and_mx.pl kevin.mcgrail@thoughtworthy.com or

perl example/check_email_and_mx.pl kevin.mcgrail@thoughtworthy.com google@google.com president@whitehouse.gov

If you supply only one email address argument, the program will exit with a exit status of 0 for a success and 1 for a failure:

perl example/check_email_and_mx.pl kevin.mcgrail@failed || echo 'This email is no good'

MIMEDEFANG
We are using this routine with MIMEDefang and have been for many months via the filter_sender hooks. For example, make a function that excludes authorized senders for your particular setup and add the following code snippets to your mimedefang-filter:

sub filter_initialize { #for Check Valid MX use Net::validMX qw(check_valid_mx); }

sub is_authorized_sender { my ($sender, $RelayAddr) = @_; 

      if ([test for authorized user]) {
        return 1;
      } else {
        return 0;
      }

}

sub filter_sender { my ($sender, $ip, $hostname, $helo) = @; my ($rv, $reason); #mdsyslog('warning', "Testing $sender, $ip, $hostname, $helo"); 

      if (&is_authorized_sender($sender, $RelayAddr)) {
        return ('CONTINUE', "ok");
      }

      if ($sender ne '<>') {
        ($rv, $reason) = &check_valid_mx($sender);
        unless ($rv) {
          md_syslog('warning', "Rejecting $sender - Invalid MX: $reason.");
          return ('REJECT', "Sorry; $sender has an invalid MX record: $reason.");
        }
      }

}

COPYRIGHT

Copyright (c) 2006 Kevin A. McGrail. All rights reserved.

This distribution, including all of the files in the Net::validMX package, is free software; you can redistribute it and/or modify it under the Perl Artistic License v1.0 available at http://www.perlfoundation.org/legal/licenses/artistic-1_0.html

perlartistic

AUTHOR INFORMATION

Kevin A. McGrail kevin.mcgrail@thoughtworthy.com

UPDATE HISTORY

v1.0 Released Oct 11, 2005. Original release for MIMEDefang filter. v2.0 Released Nov 3, 2005. Incorporated many user updates. v2.1 Released May 23, 2006. Switched to a perl Library (Net::validMX). Small efficiency change to short-circuit the DNS resolution of an IP address.
v2.2 Under Development. Clarified the LICENSE by pointing readers to the README. Added functions check_email_and_mx & check_email_validity. Expanded documentation and added check_email_and_mx & check_email_validity calls to example. Cleaned up distribution production. Changed logic to check MX records that resolve to IPs to see if it is privatized first.

HOMEPAGE

Releases can be found at http://www.thoughtworthy.com/downloads/ and on CPAN at http://search.cpan.org/~kmcgrail/.

CAVEATS

THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.

TODO

SOLVED TODO ITEMS

CREDITS

Based on an idea from Les Miksell and much input from Jan Pieter Cornet. Additional thanks to David F. Skoll, Matthew van Eerde, and Mark Damrose for testing and suggestions. And sincere apologies in advance if I missed anyone!