app/views/account_approved_mailer/account_approved_email.html.erb
<!DOCTYPE html>
<html>
<head>
<meta content='text/html; charset=UTF-8' http-equiv='Content-Type' />
</head>
<body>
<h1>Welcome to Palomacy's pigeon help, <%= @user.name %></h1>
<p>
You have been approved as a pigeon expert for our service.
your account name is: <%= @user.email %>.<br>
</p>
<p>Thanks for joining and have a great day!</p>
</body>
</html>