Add a Message to the Order Completed Email
Inserts your own paragraph, such as care instructions or a review request, above the order details in the WooCommerce "Order completed" email.
Snippet Library
Email snippets for WordPress
Snippets for the emails WordPress sends: change the sender name and address, add a Reply-To header, send HTML email and turn off notifications you do not need. For site owners who want their messages to arrive and look right.
Fix Plain Emails Sent as HTML
When a plugin switches all emails to HTML, WordPress's own plain emails arrive as one squashed paragraph with broken links; this adds line breaks and clickable links back.