There’s a great perl module Email::Valid to check if a string is a well-formed email address. It doesn’t actually check to see if the email exists in the destination domain, but in it’s simplest form we can just make sure the string follows the proper email address format specification.

Install the module:

# apt-get install -y libemail-valid-perl

quick and dirty:

#!/usr/bin/perl
use strict;
use Email::Valid;

# do it once with an email address as an argument
#if ( ! Email::Valid->address("$ARGV[0]")){print "$ARGV[0]\n"};

my $file="to_be_tested2_emails.txt";

# do it with a list of emails
  open(FH,"$file") or die("Can\'t read $file.\n");
  foreach my $line (<FH>) {
    chomp $line;
    if ( ! Email::Valid->address("$line")){print "$line\n"};

  };
  close(FH);

TODO: think of loading into array; removing malformed addresses; having option to run once vs. run list; test the rfc822 validation