cant open php file

[jashina]

i install xampp version 1.7.7.apache and mysql running nicely.
i make a sample php file to display hello world and save in xampp/htdocs folder .
it is also working nicely but i make a html file named contact wich contain a contact form and saved in the same folder as contact.html.
i saved a contact.php also in the same folder for sending the mail .
while open the html file and try to send mail getting error.
warning:mail()[function.mail]:Failed to connect to mailserver at localhost port25,verify your SMTP and smtp_port settings in php.ini or use ini_set() in c:\xampp\htdocs\contact.php on line 16
please help.