I have my following code below to send notifications, newsletters to my registered customers and its working well

my Question is that, is it really efficient and effective to send out mails to over 100k customers emails

 CGI CODE 
#!/usr/bin/perl -wT

use strict;
use warnings;
use CGI qw/:standard/;


print "Content-type: text/html\n\n";
print <<HTML;
<!doctype html>
<html lang = "en">
   <head>
      <meta charset = "utf-8">
      <title>mail sending with progressbar-jquery-ajax-</title>
      <link href = "https://code.jquery.com/ui/1.10.4/themes/ui-lightn
+ess/jquery-ui.css"
         rel = "stylesheet">
      <script src = "https://code.jquery.com/jquery-1.10.2.js"></scrip
+t>
      <script src = "https://code.jquery.com/ui/1.10.4/jquery-ui.js"><
+/script>
      
      <style>
.ajax-loader
{
    display: inline-block;
    width: 20px;
    height: 20px;
    border: 8px solid #204d74;
    border-right-color: transparent;
    border-radius: 50%;
    animation: spin 1.3s linear infinite;
}

\@keyframes spin
{
    from { transform: rotate(0deg);   opacity: 0.3; }
    50%  { transform: rotate(180deg); opacity: 1.0; }
    to   { transform: rotate(360deg); opacity: 0.3; }
}
      </style>
      
      
      
      <script>
  \$(document).ready(function () {
    \$("#Submit").click(function(event) {
    if (\$("form input[name='sub']").val() == "") {
        \$('#error').text("Subject Required");
        return false;
        }
        if (\$("form textarea[name='msg']").val() == "") {
        \$('#error').text("Message Required");
        return false;
        }
       Execute();
       \$('#error').hide();
       \$('#progress_start').show();
    });

    function Execute(){
      \$.ajax({
  xhr: function()
  {
    var xhr = new window.XMLHttpRequest();
    //Upload progress
    xhr.upload.addEventListener("ajax-loader", function(evt){
      if (evt.lengthComputable) {
        var percentComplete = evt.loaded / evt.total;
        //Do something with upload progress
        console.log(percentComplete);
      }
    }, false);
    //Download progress
    xhr.addEventListener("ajax-loader", function(evt){
      if (evt.lengthComputable) {
        var percentComplete = evt.loaded / evt.total;
        //Do something with download progress
        console.log(percentComplete);
      }
    }, false);
    return xhr;
  },
  type: 'POST',
  url: 'mail.pl',
  data: { 'sub': \$("input[name='sub']").val(), 
        'msg': \$("textarea[name='msg']").val() 
 },
  success: function(res){
    \$('#progress_start').hide();
    \$('#Response').html(res.msg);
  },
  error: function() {
          alert("Failed To send Message");
        }
});
    };

  });
</script>
   </head>
   
   <body>
   
      <br>
     <form method="post">
  <input type="text" id="sub" name="sub" placeholder="Subject"><br><br
+>
  <textarea id="msg" name="msg" placeholder="Message"></textarea><br><
+br>
  <input type="button" id="Submit" value="Submit">
</form>

<div id='progress_start' style='display:none'>
<p>Running the task<span class="ajax-loader"></span></p>
</div>
<div id="Response"></div>
<div id="error"></div>
   </body>
</html>

HTML

[download]
 Mail.pl code 
my $sub = $Cgi->param("sub");
my $msg = $Cgi->param("msg");                  

my $Response;
    
if ($sub) {        
my $select_emails = $dbh->prepare("SELECT DISTINCT email FROM testuser
+");
$select_emails->execute();
my $records = $select_emails->fetchall_arrayref;

my @to;
for my $em ( @$records ) {
    push @to, @$em;
}


for my $recipient(@to) {
    mail($recipient);
}

sub mail {
  my $recipient = shift;

my $smtpserver = 'smtp.xxxxxx.com';
my $smtpport = 587;
my $smtpuser   = 'xxxxx';
my $smtppassword = 'xxxxxx';


my $transport = Email::Sender::Transport::SMTP->new({
  host => $smtpserver,
  ssl  => 'starttls',
  port => $smtpport,
  sasl_username => $smtpuser,
  sasl_password => $smtppassword,
});

my $email = Email::Simple->create(
  header => [
    To      => $recipient,
    From    => 'xxxxx@xxxx.com',
    Subject => $sub,
    'Content-Type' => 'text/html', 
  ],
  body => $msg,
);

sendmail($email, { transport => $transport });

$Response = "Done sending";

}
my $json = encode_json(
  { msg => $Response }
);
print $Cgi->header( -type => 'application/json' ),$json;
}                                            

$dbh->disconnect;

[download]

In reply to Mail sending by frank1

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


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