WordPress - Add new columns in dashboard

functions.php

<?php
// REGISTER THE COLUMN
add_filter('manage_contatos_posts_columns', 'posts_columns');
function posts_columns($defaults){
	unset($defaults['post_date']);
	$defaults['email'] = 'E-mail';
	return $defaults;
}

// RENDER THE COLUMN
add_action('manage_contatos_posts_custom_column', 'posts_custom_columns', 5, 2);
function posts_custom_columns($column_name, $post_id){
	if($column_name === 'email'){
		echo get_post_meta($post_id,'email', true);
	}
}