If you want to terminate related emails, please log back into that other account, delete projects and toggle off the “Allow Emails” for each of the users. Open People Module in a Detailed view and navigate to Allow Emails column. See screenshot: http://screencast.com/t/tiQeewsO.
Furthermore, if you don’t do the above, all emails and the account will terminate automatically once your trial period ends, about 30 days after it was created.
All the best,