Finally i found the solution by myself
1) Create a hidden field in webform say username field.
2)then go to /webform/emails .select the component value that is equal to username hidden field you previously created.then edit added component value in E-mail from address section select the component radio button instead of Default: [email protected] radio button.
3)then create a custom module add this code
function your_module_form_alter(&$form, &$form_state, $form_id){
if ($form_id == 'your_webform_id') {
$uid = arg(1);
if ( arg(0) == 'user' && is_numeric($uid) ) {
$account = user_load($uid);
$form['submitted']['Your-hidden-field-machine-name']['#value'] = $account->mail;
}
}
}