Different solutions that've found to replace WordPress' default admin email address and name. Should be added to your theme's functions.php file.

WordPress Custom Sender Name & Email Address.php

<?php

/*
 * DESCRIPTION: All WordPress email notifications are sent from
 * [email protected] with the sender's name as "WordPress".
 * Any one of these functions should help you change that.
 *
 * Relevant WordPress core file is /wp-includes/pluggable.php
 */


// WordPress Notification Mail: Custom Sender's Email Address
add_filter('wp_mail_from','custom_email_from');
function custom_email_from($mail) {
	$mail = '[email protected]';
	return $mail;
}
// WordPress Notification Mail: Custom Sender's Name
add_filter('wp_mail_from_name','custom_email_from_name');
function custom_email_from_name($name) {
	// $name = get_option('blogname');
	$name = 'Your Name';
	return $name;
}
// CREDIT: http://wordpress.org/support/topic/564535#post-2083414



// WordPress Notification Mail: Custom Sender's Email Address
add_filter('wp_mail_from','custom_email_from');
function custom_email_from($mail) {
	return '[email protected]';
}
// WordPress Notification Mail: Custom Sender's Name
add_filter('wp_mail_from_name','custom_email_from_name');
function custom_email_from_name($name) {
	return 'Your Name';
}
// CREDIT: http://wordpress.org/support/topic/564535#post-2083414



// WordPress Notification Mail: Custom Settings
add_action('phpmailer_init', 'wp_mail_to_smtp');
function wp_mail_to_smtp(&$phpmailer) {
	$phpmailer->Sender = '[email protected]';
	$phpmailer->From = '[email protected]';
	$phpmailer->FromName = 'From Name';
}
// CREDIT: http://www.johnparris.com/customize-wordpress-email-headers/



if ( !function_exists('add_action') ) {
	header('Status: 403 Forbidden');
	header('HTTP/1.1 403 Forbidden');
	exit();
}
if ( !class_exists('wp_mail_from') ) {
	class wp_mail_from {

		function wp_mail_from() {
		add_filter( 'wp_mail_from', array(&$this, 'fb_mail_from') );
		add_filter( 'wp_mail_from_name', array(&$this, 'fb_mail_from_name') );
		}

		// new name
		function fb_mail_from_name() {
			$name = 'My Blog is my Blog';
			// alternative the name of the blog
			// $name = get_option('blogname');
			$name = esc_attr($name);
			return $name;
		}

		// new email-adress
		function fb_mail_from() {
			$email = '[email protected]';
			$email = is_email($email);
			return $email;
		}

	}
	$wp_mail_from = new wp_mail_from();
}
// CREDIT: http://wpengineer.com/1604/change-wordpress-mail-sender/

?>