File path for AJAX script (in Wordpress)

That's not the way to implement ajax in wordpress. All ajax request should be made to admin-ajax.php.

In your template file:

<script type="text/javascript">var ajaxurl = '<?php echo admin_url('admin-ajax.php'); ?>';</script>

In your js:

$.ajax({        url: ajaxurl,            type: "POST",        cache: false,        data: data + '&action=sendmail' //action defines which function to use in add_action});

in your functions.php:

function send_my_mail(){#do your stuff}add_action('wp_ajax_sendmail', 'send_my_mail');add_action('wp_ajax_nopriv_sendmail', 'send_my_mail');

Read about Ajax in Plugins.

I would be recommended to you use system like Registry for save all "global" values in a one place.

Registry design pattern

There is my small jQuery plugin if this is may be interesting to you. GitHub rep

<script type="text/javascript">    $.Registry.set('urlMail', '<?php get_bloginfo('template_url'); ?>/templates/process.php';</script>

And to get value from the Registry you must use $.Registry.get('urlMail');

I've solved using the code provided by RRikesh but replacing

data: data 

with

data: data + '&action=sendmail'