I think you're overcomplicating this problem. So here's my final attempt to explain it to you.

MIME messages are hierarchical in nature. That is to say, a MIME message can contain other MIME messages which can, in turn, also contain other MIME messages and so on. So whatever you use to parse a MIME message, can also be used to parse its children.

In fact, MIME::Parser is cleverer than that, if you set the extract_nested_messages flag to 1 (which is the default value, I'm not sure why you changed it in your code) then it will produce a tree structure containing all of the MIME messages contained within your original message. You can see the structure of this tree with the dump_skeleton method and you can get the children of any given MIME message by using the parts method.

So, you've gone as far as getting the top level message in $entity. If you change the nested messages flag to 1 then your entity will contain sub-entities which you can access using $entity->parts. Each of these contained messages will be a MIME::Entity object and you can extract various parts of the message (like the headers) using the methods described in the documentation.

Is that clearer?

Thanks for reply and your precious time.
I think you got fed up that is why you written "So here's my final attempt to explain it to you."
Any way thanks again, i got the solution, it is like this:
Store all attachment in directories then read all files one by one then do the regexp and find the hotmail addresses.
All attachment is .msg file so it becomes easy for me to identify.
I just want your opinion on this, is this solution good?
In future also there will be lot of emails will be keep coming and i need to parse those
attachment and then find the sender address. I am posting my code here.Regarding setting the flag 0 to below method extract_nested_messages, due to storing all attachment.If I set this to 1, then it doesn't stores my .msg attachment that is the main one and I need to extract header info from that only. If I set to 1 and then try to get entity->parts, it just says that mime type, whn i try to get the header info doesn't print anything. May be because i am doing something wrong or not calling the method properly. If u have time then pls. look into my code then advice. Thanks in advance.

#!/usr/bin/perl


use strict;
use Mail::POP3Client;
use MIME::Parser;
use MIME::Head;

use Mail::Header;

#usage() unless scalar @ARGV == 3;
my $pop = new Mail::POP3Client( HOST        => 'server',
                                USER        => 'my',
                                PASSWORD    => 'pass' );

my $tmp_directory = "/tmp/attach";
my $parser = new MIME::Parser;
$parser->output_dir($tmp_directory);
$parser->output_prefix("attachment");
$parser->output_to_core();
open (FH,">>/tmp/msgtxt1");
for (my $i = 1; $i <= $pop->Count(); $i++){
  my $head = $pop->Head($i);
  if ($head =~ /X-MS-Has-Attach: yes/i){
        foreach ( $pop->Head( $i ) ) {
                if( /^(Subject):\s+/i ) {
                        if ( /complaint about message from/) {
                                my $msg = $pop->HeadAndBody($i);
                                ### Automatically attempt to RFC-1522-
+decode the MIME headers?
                                $parser->decode_headers(1);           
+  ### default is false

                                ### Parse contained "message/rfc822" o
+bjects as nested MIME streams?
                                $parser->extract_nested_messages(1);  
+  ### default is true

                                ### Look for uuencode in "text" messag
+es, and extract it?
                                $parser->extract_uuencode(1);         
+  ### default is false

                                ### Should we forgive normally-fatal e
+rrors?
                                $parser->ignore_errors(0);            
+  ### default is true
                                my $entity = $parser->parse_data($msg)
+;

                                #$entity->print_header()

                                my $head = $entity->head;
                                my $msg_summary = "     Message Summar
+y for message \n" .
                                "     From   : " . $head->get('From') 
+.
                                "     To     : " . $head->get('To') .
                                "     Subject: " . $head->get('Subject
+') .
                                "     Date   : " . $head->get('Date') 
+. "\n";
                                print " -- $msg_summary \n";

                                my @parts = $entity->parts;

                                my $body;
                                my @attachments;

                                # If this is a single part message, we
+ should just append it
                                # (To be handled later)
                                unless( $entity->parts ){
 # Single part.  Just add it as a comment
                                        $body = $entity->stringify_bod
+y;
                                        #print " -- $body \n";
                                } else {
                                        # Multi-part.
                                        # Assume the first part is the
+ comment body and any additional
                                        # parts are the attachments
                                        @attachments = $entity->parts;
                                        $body = $attachments[0]->strin
+gify_body;
                                        
                                }
                                for my $attachment ( @attachments ) {
                                        my $headers = $attachment->hea
+d;
                                        print " - $attachment->bodyhan
+dle->as_string()\n";
                                        #print " --   $attachment --- 
+\n";
                                }
                                #$entity->dump_skeleton;
                                ### Get the head, a MIME::Head:

                        }
                }
        }
#        print "\n";

  }
}
close(FH);

$pop->Close();

my $dirtoget="/tmp/attach/";
opendir(IMD, $dirtoget) || die("Cannot open directory");
my @thefiles= readdir(IMD);

foreach my $fl (@thefiles) {
        if ($fl =~ m/msg/){
                &readFile($fl);
        }
}

sub readFile {

        my ($filename) = @_;
        $filename = $dirtoget.$filename;
        open(MSG,"$filename") || die ("Cannot Open File for Reading\n"
+);
        while (<MSG>) {
                my $ln = $_;
                if ($ln =~ m/^To: /){
                        print $ln;
                }

        }

        close(MSG);

}
[download]

Thanks in advance