function bp_get_the_thread_message_css_class() {
		global $thread_template;

		$classes = array();

		// Zebra-striping.
		$classes[] = bp_get_the_thread_message_alt_class();

		// ID of the sender.
		$classes[] = 'sent-by-' . intval( $thread_template->message->sender_id );

		// Whether the sender is the same as the logged-in user.
		if ( bp_loggedin_user_id() == $thread_template->message->sender_id ) {
			$classes[] = 'sent-by-me';
		}

		/**
		 * Filters the CSS classes for messages within a single thread.
		 *
		 * @since 2.1.0
		 *
		 * @param array $classes Array of classes to add to the HTML class attribute.
		 */
		$classes = apply_filters( 'bp_get_the_thread_message_css_class', $classes );

		return implode( ' ', $classes );
	}