app/views/admin_mailer/send_approved_email.html.erb
<!DOCTYPE html>
<html>
<head>
<meta content='text/html; charset=UTF-8' http-equiv='Content-Type' />
</head>
<body>
<h1>Welcome to CS169 EnrollMe, <%= @user.name %></h1>
<p>
The admin has successfully approved your team's enrollment into CS169.
</p>
<p>
To login to the site, just follow this link: <%= @url %>.
</p>
<p>Thanks for joining and have a great day!</p>
</body>
</html>