I am trying to utilize a mailer during my WordPress theme, however i don't appear to have the ability to pull admin email from WordPress.

I've got a mailer.php file during my theme folder and attempted using get_bloginfo('admin_email') function however it does not work. I am a PHP newbie, but I am speculating the mailer.php file is not "connected" to WordPress installation. I attempted including it within the functions.php file, however it only triggered my theme to visit blank.

So my real question is, how do you pull WordPress functions in files, that are not theme files?

To reply to Pekka's comment - I recieve a mistake: Fatal error: Call to undefined function get_bloginfo() in mailer.php online 4

Import WordPress's functions using

include "/path/to/your/wordpress/wp-blog-header.php";

Next, you'll have the ability to call get_bloginfo().