WooCommerce - Add Select Field To Check Out and then Route to specific mail.

for-functions.php

<?php
/**
 * Add the field to the checkout
 **/
add_action('woocommerce_after_order_notes', 'my_custom_checkout_field');

function my_custom_checkout_field( $checkout ) {

    echo '<div id="my_custom_checkout_field"><h3>'.__('My Field').'</h3>';

    woocommerce_form_field( 'my_field_name', array(
        'type'          => 'select',
        'class'         => array('my-field-class form-row-wide'),
	'required' 		=> true,
        'label'         => __('Fill in this field'),
        'placeholder'       => __('Enter something'),
	'options'     => array(
        'choice1' => __('choice1', 'woocommerce' ),
        'choice2' => __('choice2', 'woocommerce' )
        )
        ), $checkout->get_value( 'my_field_name' ));

    echo '</div>';

}

/**
 * Process the checkout
 **/
add_action('woocommerce_checkout_process', 'my_custom_checkout_field_process');

function my_custom_checkout_field_process() {
    global $woocommerce;

    // Check if set, if its not set add an error.
    if (!$_POST['my_field_name'])
         $woocommerce->add_error( __('Please enter something into this new shiny field.') );
}

/**
 * Update the order meta with field value
 **/
add_action('woocommerce_checkout_update_order_meta', 'my_custom_checkout_field_update_order_meta');

function my_custom_checkout_field_update_order_meta( $order_id ) {
    if ($_POST['my_field_name']) update_post_meta( $order_id, 'My Field', esc_attr($_POST['my_field_name']));
}