What have you done to try and debug it?

My starting point would be to test it outside of the CGI environment: it is far easier to debug things that way.

I note that you have a function called sendmail, and you also import a function called sendmail, and you call sendmail(...) inside your sendmail function. Your own defined function will override the imported one, so this will lock you into infinite recursion on your own function. In a command-line environment you'd see a warning from defining a function with the same name; I suspect that in your CGI environment it is trying to show you those warnings, but it's saving them up to send to the browser and due to the infinite loop never getting to the point it actually sends them.

If your sendmail function took its inputs as arguments, and verified them, you might also have had a chance to spot something was wrong and bail out: that's a benefit of using better design.

i tried to debug but i get no any error which has made me also get confused, even if i take the script to command line there is no error, after running the script

You never call getready or sendmail. How do you think you kick off the mail sending?

"i tried to debug..."

How? Genuinely curious, because you don't seem to grasp the fundamentals of what you've written. Tutorials->Debugging and Optimization->Basic debugging checklist, among others.

there is no error

Does the script exit?

I suspect not.

I haven't tried running your script but it looks to me like you have an infinite loop. So the script goes round and round merrily executing forever without error because it is doing what the code says it should. If the code runs but doesn't do what you want it to, that's not an error, it's a bug!

The code consist of some setup and then three sub's which never get called. Well, sendmail gets called within getready, but no one calls getready...
When I comment out the DBI code (since I don't have your database) and run the script, it prints out

Content-type: text/html
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and exits, just as expected.

thats the best i tried, coz i thought when i call sendmail. the sending process will start.

Not directly related to your mail sending issue but I'm including it because I always find it helpful when people make constructive criticism of my code...

Your script makes use of CGI::Carp through

use CGI::Carp qw(fatalsToBrowser warningsToBrowser);
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The warning manifests as an HTML comment in the webpage at the point you call the warningsToBrowser(); method. It is usually best to do it at the end so the warning appears at the bottom of the HTML source code. This saves you having to hunt for it!

It might help to link to the old discussion:

[id://11155744] -> Send email with recipient name

From How to link which is always listed in the help section below the post form:

Linking to a specific node by node_id:

Now you can link to a specific node_id by using [id://979] which will make a link like vroom. You can also follow it up with link text that you want to use in place of the node title like so [id://131|The Default Page] whic creates a link like so: The Default Page

Crossposting is allowed, but it's considered polite to announce it to prevent people not visiting both sites from hacking on a problem already solved at the other end of the internet.

Posting exactly the same code, ignoring all responses already provided, https://www.youtube.com/watch?v=lOTyUfOHgas.

i have fixed my script and working very well now. without any help from anyone. i just went through each sub function to make sure each works

wat was confusing me is that. i thought i can just call only 1 function and leave others behind and run themselves on script execution

Now my mine point is to work on this script efficacy and effective to deliver msg to over 100k receivers

Anyone want to addone something, so it become more effective on delivering msg to 100k, i appreciate

#!/usr/bin/perl -wT


use lib '.';
use warnings;
use DBI;
use Email::Sender::Simple qw(sendmail);
use Email::Sender::Transport::SMTP ();
use Email::Simple ();
use Email::Simple::Creator ();
use CGI qw/:standard/;
use CGI::Carp qw(fatalsToBrowser warningsToBrowser);

$CGI::DISABLE_UPLOADS = 1;
$CGI::POST_MAX        = 1048576;


print "Content-type: text/html\n\n";


my $host =   "xxxxx";
my $usr =    "xxxxx";
my $pwd =    "xxxxx";
my $dbname = "xxxxx";

my $dbh = DBI->connect("DBI:mysql:$dbname:$host", $usr, $pwd, {
                                  RaiseError => 1,
                                  }) or die $DBI::errstr;





sub getusers {
my $sth = $dbh->prepare("SELECT * FROM bmop");
$sth->execute();

    while (my @row = $sth->fetchrow_array) {
        $name = $row[2]; # Get their names
        $rcpt = $row[5]; # Get their emails
        push @names,$name;
        push @rcpts,$rcpt;

    }
}
getusers();

sub getready {
    my $j = 0;

    foreach my $i(@names){
            ## Grab user info from the table

        $rcv_names = $names[$j]; # Get their name
        $rcv_emails = $rcpts[$j]; # Get their email
        mail();
        $j++;

    }

 }
 
getready();


sub mail {

my $sub = "Test mail";
my $msg = "<p> Hi $rcv_names </p>";

my $smtpserver = 'xxxx';
my $smtpport = 587;
my $smtpuser   = 'xxxxx';
my $smtppassword = 'x+x+x+';


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      => $rcv_emails,
    From    => 'xxxxx@xxxxx.com',
    Subject => $sub,
    'Content-Type' => 'text/html', 
  ],
  body => $msg,
);

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

}
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