Transactional and Notificational Emails trigger hooks :)

woocommerce.md

Order Statuses:

'wc-pending'    => _x( 'Pending payment', 'Order status', 'woocommerce' ),
'wc-processing' => _x( 'Processing', 'Order status', 'woocommerce' ),
'wc-on-hold'    => _x( 'On hold', 'Order status', 'woocommerce' ),
'wc-completed'  => _x( 'Completed', 'Order status', 'woocommerce' ),
'wc-cancelled'  => _x( 'Cancelled', 'Order status', 'woocommerce' ),
'wc-refunded'   => _x( 'Refunded', 'Order status', 'woocommerce' ), // Excluded
'wc-failed'     => _x( 'Failed', 'Order status', 'woocommerce' ), // Excluded

Trigger email hook concept:

New Order - Recipient(s)

New order emails are sent to chosen recipient(s) when a new order is received.

• Pending|Failed -> Processing
• Pending|Failed -> Completed
• Pending|Failed -> On hold

Cancelled order - Recipient(s)

Cancelled order emails are sent to chosen recipient(s) when orders have been marked cancelled (if they were previously processing or on-hold).

• Processing -> Cancelled
• On hold -> Cancelled

Failed order - Recipient(s)

Failed order emails are sent to chosen recipient(s) when orders have been marked failed (if they were previously processing or on-hold).

• Pending -> Failed
• On hold -> Failed

Order on hold - Customer

This is an order notification sent to customers containing order details after an order is placed on-hold.

• Pending -> On hold
• Failed -> On hold

Processing order - Customer

This is an order notification sent to customers containing order details after payment.

• Pending -> Processing
• On-hold -> Processing
• Failed -> Processing

Completed order - Customer

Order complete emails are sent to customers when their orders are marked completed and usually indicate that their orders have been shipped.

Please Note: It has nothing to do so it triggers on woocommerce_order_status_completed when status is completed.

Customer invoice - Customer

Customer invoice emails can be sent to customers containing their order information and payment links.

Please Note: It is always manually sent.