From: WordPress [wordpress@siteurl.com]
Subject: [site name] Your user name and password
Message:
         username: user
         Password: password
         siteurl.com/wp-login.php

From: My Site Name [info@siteurl.com]
Subject: siteurl.com customer account activated
Message:
       Your customer account has been activated.

       Your Login credentials are:

       Username: user email
       Password: password

       Thanks,
       abcd

<?php
/**
 * Plugin Name: Custom new user notification email
 * Description: Overwrites the pluggable 'wp_new_user_notification()' plugin to allow the sending of a custom email
 * Author: David Gard
 * Version: 1.0
 */

if ( !function_exists('wp_new_user_notification') ) :
/**
 * Pluggable - Email login credentials to a newly-registered user
 *
 * A new user registration notification is also sent to admin email.
 *
 * @since 2.0.0
 *
 * @param int    $user_id        User ID.
 * @param string $plaintext_pass Optional. The user's plaintext password. Default empty.
 */
function wp_new_user_notification($user_id, $plaintext_pass = ''){

    $user = get_userdata($user_id);

    // The blogname option is escaped with esc_html on the way into the database in sanitize_option
    // we want to reverse this for the plain text arena of emails.
    $blogname = wp_specialchars_decode(get_option('blogname'), ENT_QUOTES);

    $message  = sprintf(__('New user registration on your site %s:'), $blogname) . "rnrn";
    $message .= sprintf(__('Username: %s'), $user->user_login) . "rnrn";
    $message .= sprintf(__('E-mail: %s'), $user->user_email) . "rn";

    @wp_mail(get_option('admin_email'), sprintf(__('[%s] New User Registration'), $blogname), $message);

    if ( empty($plaintext_pass) )
        return;

    $message  = sprintf(__('Username: %s'), $user->user_login) . "rn";
    $message .= sprintf(__('Password: %s'), $plaintext_pass) . "rn";
    $message .= wp_login_url() . "rn";

    wp_mail($user->user_email, sprintf(__('[%s] Your username and password'), $blogname), $message);

}
endif;