Send email in PHP using the mail function. Note the envelop wrapper includes the -f from address to ensure delivery.

sendEmail.php

/**
 * sendEmail
 * 
 * @param string $to
 * @param string $from
 * @param string $replyto
 * @param string $cc
 * @param string $bcc
 * @param string $subject
 * @param string $body
 */
public static function sendEmail(
    $to = false, $from = false, $replyto = false, $cc = false, $bcc = false, $subject = false, $body = false
)
{
    // Email Headers
    $headers   = array();
    $headers[] = "MIME-Version: 1.0";
    $headers[] = "Content-type: text/html; charset=iso-8859-1";
    if (!empty($from)) {
        $headers[] = "From: " . $from;
    }
    if (!empty($cc)) {
        $headers[] = "Cc: " . $cc;
    }
    if (!empty($bcc)) {
        $headers[] = "Bcc: " . $bcc;
    }
    if (!empty($replyto)) {
        $headers[] = "Reply-To: " . $replyto;
    }
    $headers[] = "Subject: " . $subject;
    $headers[] = "X-Mailer: PHP/" . phpversion();
    $headers[] = "";
    
    // Mail it
    try {
        mail($to, $subject, $body, implode("\r\n", $headers), '-f '.$from);
        return true;
    } catch (\Exception $e) {
        trigger_error('Unable to send email. ' . $e->getMessage(), E_USER_WARNING);
        return false;
    }
}