You can send an unlimited number of emails per day; however, there is a limit to the number of recipients you can include in each email. When you select to send your email to an email list you have created in your address book, you can send your email to up to 2,500 recipients with a single click.
When you manually enter/paste/select addresses, either from email addresses you manually enter or from your address book, you can send your email to up to 250 recipients. If you have a bigger list then simply copy the email you just sent and send it to the next 250 people on your list. You can do this as many times as you like until all your emails have been sent. To make this process easy - you have the option to "Copy Email" after each email is sent.)