Just while submitting the form give action to controller like:
<?php echo Mage::getUrl()?>bpartner/index/mailbpartner
bpartner your module name
Index your controller name
mailbpartner your function in INDEX NAMED CONTROLLER FILE.
Get all details through POST and send mail like below + redirect with success
$to = "abc@abc.com";
$dt = date('d-m-Y');
$subject = "Become A Partner Details on date $dt";
$mail = new Zend_Mail('utf-8');
$mail->setBodyHtml($message)
->setFrom($data['email'], $data['firstname'])
->addTo($to, 'Site Admin')
->setSubject($subject);
try {
$mail->send();
Mage::getSingleton('core/session')->addSuccess('Mail sent successfully. We will contact you shortly');
}
catch(Exception $e) {
Mage::getSingleton('core/session')->addError('Unable to send email.');
}
$this->_redirect('bpartner');
Some above data are POST DATA which is self understandable