Secure e-mail systems

[Pengyou]

What is the most secure e-mail system? I am choosing a linux webhost. The ideal solution will not only be very secure but very simple for users to use. Please specify if used on webmail or with a client, i.e. Outlook, Thunderbird, etc

Thanks

Tom

[Stephen Philbin]

What exactly do you mean by "secure e-mail system"?