Php mail() vs Yahoo: Can someone Simply Explain Steps required for YAHOO to receive mail from php mail function?

Question 1

I Finally got a laaaaarge smile on my face. Working together with @DaveRandom, He helped me come up with these codes:

NOTE: The code bellow uses PHPMailer

    <?php

            $senderName = 'Erick Best'; //Enter the sender name
            $username = 'erickbestism@yahoo.com'; //Enter your Email
            $password = 'passwordHere';// Enter the Password


            $recipients = array(
                'erickbestism@gmail.com' => 'Erick Best',
                'erickbestism@yahoo.com' => 'Yahoo User',
            );
          ///That's all you need to do

//No need to edit bellow    
            require '../PHPMailerAutoload.php';

            //Create a new PHPMailer instance
            $mail = new PHPMailer();

            // Set up SMTP
            $mail->IsSMTP();
            $mail->SMTPAuth   = true;
            $mail->SMTPSecure = "tls";
            $mail->Host       = "smtp.mail.yahoo.com";
            $mail->Port       = 587; // we changed this from 486
            $mail->Username   = $username;
            $mail->Password   = $password;

            // Build the message
            $mail->Subject = 'PHPMailer mail() test';
            $mail->msgHTML(file_get_contents('contents.html'), dirname(__FILE__));
            $mail->AltBody = 'This is a plain-text message body';
            $mail->addAttachment('images/phpmailer_mini.gif');

            // Set the from/to
            $mail->setFrom($username, $senderName);
            foreach ($recipients as $address => $name) {
                $mail->addAddress($address, $name);
            }

            //send the message, check for errors
            if (!$mail->send()) {
                echo "Mailer Error: " . $mail->ErrorInfo;
            } else {
                echo "Message sent!";
            }

        ?>

And this WORKED like VOODOO!... It sent mails to any provider. Including **YAHOO**

Hope it helps someone!

Question 2

try this:

<?php 
include("Mail.php"); 

$recipients = "mailto@example.com"; 

$headers["From"]    = "mailfrom@example.com"; 
$headers["To"]      = "mailto@example.com"; 
$headers["Subject"] = "Test message"; 

$body = "TEST MESSAGE!!!"; 

$params["host"] = "example.com"; 
$params["port"] = "25"; 
$params["auth"] = true; 
$params["username"] = "user"; 
$params["password"] = "password"; 

// Create the mail object using the Mail::factory method 
$mail_object =& Mail::factory("smtp", $params); 

$mail_object->send($recipients, $headers, $body); 
?>

where username and password are for a yahoo account.