How to preview the order confirmation email of an order

[Anandhan]

How to preview the order confirmation email sent to the customer from the order page?

I have customized the order confirmation email template to display the order thank you note instead of the default thank you note "We're getting your order ready to be shipped. We will notify you when it has been sent.", if the customer placed the "Backorder" tagged products and the template preview shows the correct message for the "Backorder" tagged product. But the customer received an email with the default thank you message https://prnt.sc/RmvKY1cqMqsS if placed the "Backorder" product. Please advise.

Below is the template code for message

{% case delivery_method %}
  {% when 'pick-up' %}
    You’ll receive an email when your order is ready for pickup.
  {% when 'local' %}
    Hi {{ customer.first_name }}, we're getting your order ready for delivery.
  {% else %}
    {% comment %} start custom code for backorder {% endcomment %}
    {% assign line_title = '' %}
    {% assign found_backorder_item = false %}
    {% assign line_count = subtotal_line_items.size %}
    {% for line_item in subtotal_line_items %}
      {% if line_item.product.tags contains 'Backorder' %}
        {% assign found_backorder_item = true %}
        {% if line_item.product.title %} 
          {% assign line_title = line_item.product.title %}  
        {% else %}  
          {% assign line_title = line_item.title %}  
        {% endif %}
        {% break %}
      {% endif %}
    {% endfor %}
    {% if found_backorder_item == true and line_count > 1 %}
      Just a reminder that the {{ line_title  }} are on backorder and expected to ship July 7th. Any other items will ship as per normal shipping dates. We appreciate your patience and will notify you when each package ships out.
    {% elsif found_backorder_item == true and line_count == 1 %}
      The {{ line_title }} are on backorder and expected to ship July 7th. We appreciate your patience and will notify you when your order ships out.
    {% else %}
      We're getting your order ready to be shipped. We will notify you when it has been sent.
    {% endif %}
    {% comment %} end custom code for backorder {% endcomment %}
{% endcase %}