They do indeed seem to have moved (or hidden) the old email clients. I don't use them myself, except when traveling without my laptop. On my regular PC, I find it a lot easier to install and use an email client such as Thunderbird or Outlook (there are many others) -- you may want to consider that, as they're generally a lot easier to use, and more powerful.
Anyway, if you want to continue using one of those built-in clients, maybe the best thing is to open a support ticket and find out what the story is (whether you need to install a client). Perhaps you could share with us the results? And thanks for the Heads Up that the old clients seem to be gone.