mail error

I am using php 4 with apache in windows. I created a form in html with this code: <FORM method="POST" action="do_feedback.php"> <p>your name: <INPUT type="text" NAME="sender_name" size=30></p> <p>your email: <INPUT type="text" NAME="sender_email" size=30></p> <p>Additional message:<br> <textarea name="message" cols=30 rows=5></textarea> </p> <INPUT type="submit" value="Send"> </FORM> In php, I wrote this and save as do_feedback.php: <?php $msg = "Sender's Full Name:\t$sender_name\n"; $msg .="Sender's E-mail:\t$sender_email\n"; $msg .="Additional Message:\t$message\n\n"; $mailheaders = "From: My Web Site\n"; $mailheaders .="Reply-To: $sender_email\n\n"; mail("merry_e_k@yahoo.com", "Feedback Form", $msg, $mailheaders); echo "<H1 align=center>Thank You, $sender_name</H1>"; echo "<P align=center>We appreciate your feedback</P>"; ?> I got an error message ssy Undefined variable:sender_name bla bla bla and Warning: mail(): Failed to connect to mailserver at "localhost" port 25, verify your "SMTP" and "smtp_port" setting in php.ini or use ini_set() in c:\program files\apache group\apache\htdocs\do_feedback.php on line 12 what's that means? Is anyone got a clue. please help