No. A user can have multiple email accounts. Thus, an email account is one of your email accounts you connect to mailivery.
If you want to connect multiple email accounts, you've got to increase the number of email accounts available to you during the checkout process.
John Doe becomes a Mailivery user.
He owns 2 email accounts, email@example.com and firstname.lastname@example.org.
If he wants to connect both of his email accounts to Mailivery, he'd have to select "2 email accounts" during the checkout process.