functions.php

<?php

/**
 * Add "Email Us" link to footer
 *
 * @author Bill Erickson
 * @link http://www.billerickson.net/overriding-options-and-meta
 */
function be_email_us() {
	echo '<p><a href="mailto:' . get_option( 'admin_email' ) . '">Email Us</a></p>';
}
add_action( 'wp_footer', 'be_email_us' );

/**
 * Modify Author Email option on Single Posts
 *
 * @author Bill Erickson
 * @link http://www.billerickson.net/overriding-options-and-meta
 *
 * @param string $email
 * @return string
 */
function be_post_author_email( $email ) {
	global $post;
	if( is_single() )
		$email = get_the_author_meta( 'user_email', $post->post_author );
		
	return $email;
}
add_filter( 'pre_option_admin_email', 'be_post_author_email' );