A box you own and control.
Gmail is NOT secure OR private.
I don't expect hotmail, yahoo, etc. to be so either.
Also, a few times hotmail released new versions of their web interface,
they only worked for IE for about a week or two.
As long as you don't own and control the mail server, someone else has
physical access to it; hence it's not really secure.
Personally, I run my own mail server on a VPS I rent (to ARP Network, by
the way). Not the BEST of choices, but I sure trust them more than GOOGLE.
If you *really* need privacy for emails, start using something like GPG.
