email_send.php

<?php
    // Import PHPMailer classes into the global namespace
    // These must be at the top of your script, not inside a function
    use PHPMailer\PHPMailer\PHPMailer;
    use PHPMailer\PHPMailer\SMTP;
    use PHPMailer\PHPMailer\Exception;

    // Load Composer's autoloader
    require 'vendor/autoload.php';

    // Instantiation and passing `true` enables exceptions
    $mail = new PHPMailer(true);

    try {
        //Server settings
        $mail->SMTPDebug = SMTP::DEBUG_SERVER;                      // Enable verbose debug output
        $mail->isSMTP();                                            // Send using SMTP
        $mail->Host       = 'smtp.gmail.com';                    // Set the SMTP server to send through
        $mail->SMTPAuth   = true;                                   // Enable SMTP authentication
        $mail->Username   = '';                     // SMTP username
        $mail->Password   = '';                               // SMTP password
        $mail->SMTPSecure = PHPMailer::ENCRYPTION_STARTTLS;         // Enable TLS encryption; `PHPMailer::ENCRYPTION_SMTPS` also accepted
        $mail->SMTPOptions = array(
            'tls' => array(
            'verify_peer' => false,
            'verify_peer_name' => false,
            'allow_self_signed' => true
            )
        );
        $mail->Port       = 587;                                    // TCP port to connect to

        //Recipients
        $mail->setFrom('abc@gmail.com');
        $mail->addAddress($_POST['to']);

        // Content
        $mail->isHTML(true);                                  // Set email format to HTML
        $mail->Subject = $_POST['subject'];
        $mail->Body    = $_POST['body'];

        $mail->send();
    } catch (Exception $e) {
        echo "Message could not be sent. Mailer Error: {$mail->ErrorInfo}";
    }