Yes, you can immediately start sending emails once you create your account and verify the email-sending domain. Steps to verify the domain is mentioned here. 

You will be allocated 1 free credit with 1 month validity, as soon as you create your account. This credit allows you to send 10,000 emails with a cap of 100 emails per day. 

To continue sending emails and to purchase further credits, you should get your account reviewed. To review your account, fill up the customer validation form available on the left pane and submit it to us. Our team will verify the information and review your account.