This can be done but you have to change a setting in your Account Settings beforehand.
Taken from Google FAQ
Changing the HTTPS setting
We've recently made the 'Always use
https' setting the default behavior in
Gmail (the default used to be http).
Here's some background: If you sign in
to Gmail via a non-secure Internet
connection, like a public wireless or
non-encrypted network, your Google
account may be more vulnerable to
hijacking. Non-secure networks make it
easier for someone to impersonate you
and gain full access to your Google
account, including any sensitive data
it may contain like bank statements or
online log-in credentials.
Accordingly, we enable the 'Always use
https' option in Gmail by default.
HTTPS, or Hypertext Transfer Protocol
Secure, is a secure protocol that
provides authenticated and encrypted
To disable or re-enable this feature
- Sign in to Gmail.
- Click Settings at the top of any Gmail page.
- Set 'Browser Connection' to 'Don't use https' or 'Always use https.'
- Click Save Changes.
- Manually change the URL to http://mail.google.com to start
accessing Gmail via http.
Please note that selecting 'Always use
https' will prevent you from accessing
Gmail via HTTP (Hypertext Transfer
Protocol). If you trust the security
of your network, you can turn this
feature off at any time.
If you use a public computer to check
your email, it's also important to end
each of your Gmail sessions by
clicking Sign out at the top of any
Gmail page and to close all Gmail