From the Jobs / Orders List, select the checkboxes next to the orders that you would like to send emails to. Then, click the 'Email' button. (Limited to the amount of records displayed on your Jobs / Orders List, maximum 100).
In the right-hand menu, orders will be grouped together based on their order status. For each order status, you will then have the option to select which email and invoice templates to email to your clients!
Once you've chosen your email and invoice templates to send, click 'Send'!