How to add welcome message for new users?

This snippet will add welcome message on user register when you are using BuddyPress in your website. It will work with BP Better Messages plugin perfectly. If you are running BP Better Messages without BuddyPress plugin, this will not work.

function bp_messages_welcome_message( $user_id, $key, $user ){
    if ( ! function_exists( 'messages_new_message' ) ) return false;

    $args = array(
        'sender_id'  => 1,
        'thread_id'  => false,
        'recipients' => $user_id,
        'subject'    => 'Welcome to WordPlus.org',
        'content'    => "<strong>Welcome to WordPlus.org</strong>\n\n If you have any question about <strong>BP Better Messages</strong> you can ask it here directly.",
        'date_sent'  => bp_core_current_time()
    );

    $result = messages_new_message( $args );
}
add_action('bp_core_activated_user', 'bp_messages_welcome_message', 10, 3);