Your entire account cannot exceed 10MB of files uploaded to our servers and 10 GB of bandwidth usage. We also limit you to between 50,000 – 300,000 emails per month depending on which account you choose.
Remember that this doesn’t include files such as videos hosted off site on Vimeo or YouTube. Plus only some of our tools result in emails being sent – and if you do go over we simply charge you a tiny 0.0015 USD per extra email.
Full details are in the terms.