A secure e-mail client?

[Caolr]

I am looking to find a semi-secure e-mail client, yet, I can't find anything that matches what I need. Maybe they do and they just don't announce it?

I need an e-mail client that is password protected and requested every time it is opened. I want it to either encrypt stored e-mails or not store e-mails at all. I would also like it if it could still alert when new-mail arrives, but this is much less of a concern. (I do not need to send encrypted mail nor receive it).

Is there an e-mail client that has such features?

 

[Rukbat]

There are apps that allow you to password protect other apps, and if you delete email from a POP3 account on one device it's still on the server for other devices to read. I don't think you'll get closer than that until someone writes the app you want.

 

[NQuateman]

If you're using a Microsoft Exchange, I'm pretty sure that Touchdown covers your requests.