You will receive an email verifying the fax was sent. If it was not successfully sent you will also receive an email letting you know it was unsuccessful. Additionally, you can log into your account and click on the “Sent Faxes” folder. Hovering over any thumbnail will reveal the time the fax was received. If you do not see your fax in the "Sent Faxes" folder, there is something wrong with the procedure you are using to send faxes. Please reread how to send faxes.
If you do not receive an email, see this article about not receiving emails.