Perl Script for Email validation?

Question

I've created a perl script to validate email ids for my marketing team to send campaigns.

The script is behaving erratically.

For Example, I had validated 135 email ids on various dates,

******************************************
Date   |    Valid     | Invalid  | Total
******************************************
23-Dec-13    45       |   90     | 135
******************************************
24-Dec-13    90       |   45     | 135
******************************************
25-Dec-13    133      |   02     | 135
******************************************

I'm unable to figure out where it went wrong,

Link to code

Code:

 #!/usr/bin/perl
 use Data::Dumper;

 %lookup_cache = ();

 sub valid_address {
   my($addr) = @_;
   my($domain, $valid);

   # Lower-case address
   $addr = lc($addr);

   # Validate format of address
   return(0) unless ($addr =~ /^[^@]+@([-\w]+\.)+[a-z]{2,4}$/);

   # Grab domain
   $domain = (split(/@/, $addr))[1];

   # Lookup and return cached result if it exists
   $cached_result = $lookup_cache{$domain};
   if ($cached_result ne '')
   {
     #print "[cached_result] ";
     return $cached_result;
   }

   # Do domain lookup
   $valid = 0;
   if (open(DNS, "nslookup -q=any $domain |"))
   {
     while (<DNS>) {
       $valid = 1 if (/^$domain.*\s(mail exchanger|internet address)\s=/i);
     }
   }

   # Store cached result for later
   $lookup_cache{$domain} = $valid;

   return $valid;
 }

 while (<>) {
   $addy = $_;
   $addy =~ s/\s+$//;
   if ($addy)
   {
     print "$addy " . (valid_address($addy) ? 'valid' : 'invalid') . "\n";
   }
 }

Answer 1

I'd recommend using strict and warnings in all Perl scripts.

Ask for mail exchanger records with nslookup -q=MX to make the script stable. The output of nslookup -q=any might include the MX record but not always (I suppose it returns any record type it finds, not necessarily MX?).

Edit: This script works for me:

#!/usr/bin/perl

use strict;
use warnings;
use Data::Dumper;

my %lookup_cache = ();

sub valid_address {
  my($addr) = @_;
  my($domain, $valid);

  # Lower-case address
  $addr = lc($addr);

  # Validate format of address
  return(0) unless ($addr =~ /^[^@]+@([-\w]+\.)+[a-z]{2,4}$/);

  # Grab domain
  $domain = (split(/@/, $addr))[1];

  # Lookup and return cached result if it exists
  my $cached_result = $lookup_cache{$domain};
  if (defined $cached_result)
  {
    return $cached_result;
  }

  # Do domain lookup
  $valid = 0;
  if (open(DNS, "nslookup -q=MX $domain |"))
  {
    while (<DNS>) {
      $valid = 1 if (/^$domain.*\s(mail exchanger|internet address)\s=/i);
    }
  }

  # Store cached result for later
  $lookup_cache{$domain} = $valid;

  return $valid;
}

while (<>) {
  my $addy = $_;
  $addy =~ s/\s+$//;
  if ($addy)
  {
    print "$addy " . (valid_address($addy) ? 'valid' : 'invalid') . "\n";
  }
}

Answer 2

Email address syntax can be quite complicated. So, validation could be tricky - very easy to go wrong. I suggest exploring a proper library on CPAN.

Email::Valid seems to support domain checks and TLD checks too. Disclaimer: I have not used this module personally but it seems to be actively maintained.

The output of nslookup might have changed between multiple runs of the script, so your script might be reporting inconsistent results. I would suggest adding more log statements so that you can pin point what is going on.