WooCommerce: Add Content to a Specific Order Email
if ( $email->id == 'cancelled_order' ) {}
if ( $email->id == 'customer_completed_order' ) {}
if ( $email->id == 'customer_invoice' ) {}
if ( $email->id == 'customer_new_account' ) {}
if ( $email->id == 'customer_note' ) {}
if ( $email->id == 'customer_on_hold_order' ) {}
if ( $email->id == 'customer_refunded_order' ) {}
if ( $email->id == 'customer_reset_password' ) {}
if ( $email->id == 'failed_order' ) {}
if ( $email->id == 'new_order' ) {}