When you use all of your pages, you'll see a message when you log in to your Fax Thru Email account. If you attempt to send a fax using the remote faxing option, your email bounces back with a message indicating your account is out of pages. If someone sends a fax to your Fax Thru Email number and you are out of pages, the fax is dropped and you receive a notice that you are out of pages in your account.
If you would like to add pages to your account, see Adding Pages to Your Fax Thru Email Account.