If you are looking to use the portal to send out invoices to your clients, you can email your client with the invoice directly from the portal.
Click on the Work tab and click the 'Options' button on the right hand side next to the invoice you wish to email to your client.
From the drop down menu, choose 'Email Invoice' and the email slider will appear.
Providing if you are happy with the content, click on Send Email. This will send the email and a copy of the pdf invoice to the email address stated at the top of the pop up screen.