rewriting http --> https not working

[Matt Morgan]

I thought I understood how to use apache's rewriting rules to force
certain pages to https, but it's not working. I've compared my .conf
file to others online, and it looks right to me.

This is my /etc/httpd/conf.d/force-ssl.conf file:
-------
# Rewrite Rules.
RewriteEngine On
RewriteCond %{HTTPS} !=on
RewriteRule ^/webmail/(.*) https://%{SERVER_NAME}/webmail/$1 [R,L]
RewriteRule ^/mailman/(.*) https://%{SERVER_NAME}/mailman/$1 [R,L]

#Debug rewrite rules
RewriteLog /etc/httpd/logs/rewrite_engine_log
RewriteLogLevel 3
-------
The idea is to take any URL under /webmail or /mailman and redirect it
to https, so that, for example,

http://www.concretecomputing.com/webmail/

gets redirected to the same page, but using https. It doesn't happen.

SSL is working; if I type in the https it works fine. But no
redirection is happening. I have restarted Apache uneventfully. What
did I do wrong?

Thanks,
Matt