Mail sent message comes but mail does not appear in inbox or spam?

Question

Below is my mail code. when php script will execute below sent alert message shows on screen but mail not received in inbox or spam. I am not getting where i m wrong? Please anybody can help me?

               $from_mail = "tdiesel.dinpl.com/new";
                /* Email functionality */

                $to = "m.ajinkya@drushti.in";        
                $subject = "Registration Complete";
                $message = "<br><br>Following are the account details.<br><br>";

                $message .= "<table border='1'>";

                $message .= "<tr>";
                $message .= "<td><b>Customer Name :</b></td><td>$dealer_username</td>";
                $message .= "</tr>";

                $message .= "<tr>";
                $message .= "<td><b>Password :</b></td><td>$dealer_password</td>";
                $message .= "</tr>";

                $message .= "</table>";

                $message .= "<br>";    
                $message .= "<br>Regards,<br>";
                $message .= "Team| Trident Diesel Pvt. LTD.<br>";
                $message .= "Web- www.tdiesel.dinpl.com/new<br>"; 
                $message .= "Contact – +91- 20-25290018<br>";                                                
                $headers = "From: $from_mail" . "\r\n";
                $headers .= "MIME-Version: 1.0" . "\r\n";
                $headers .= "Content-type:text/html;charset=UTF-8" . "\r\n";

                /* Send mail function for Merchant */
                $mail_send = mail($to,$subject,$message,$headers);
                if($mail_send)
                {
                    echo "<script>alert('Sent')</script>";
                }
                else
                {
                    echo "<script>alert('Not Sent')</script>";
                }