[imp] Always SSL connection

[arwen at ezballet.com]

In Internet Explorer,
type webmail.mydomain.com

It will redirect to http://webmail.mydomain.com

But I want to redirect to https://webmail.mydomain.com

i.e. Always use SSL connection for webmail.

If users type http://webmail.mydomain.com I want to redirect to 
https://webmail.mydomain.com too.

Is it possible to do so through DNS settings or?

If it is impossible,
I want to disable http://webmail.mydomain.com
Only allow users to connect to https://webmail.mydomain.com

My Hosting provider told me that I have to do so in 
/etc/httpd/conf/httpd.include
Any idea on how to do so?

What I want to do is always use SSL for webmail (IMP),

Thanks so much.