How to make mod_rewrite work transparently?

Question

Following is the content of .htaccess file

<IfModule mod_rewrite.c>
  Options +FollowSymLinks
  Options +Indexes
  RewriteEngine On
  RewriteBase /
  RewriteCond %{HTTP_HOST} ^(.+)\.oomail\.org$ [NC]
  RewriteRule ^(.*)$ http://oomail.org/%1 [L]
</IfModule>

My purpose is to map all subdomain to folder. For example if a1.oomail.org is opened it should show the content of oomail.org/x1 But URL should not change.
But whenever I open a1.oomail.org URL is automatically getting changed. How can I prevent it?

Answer 1

You can't use absolute urls

RewriteCond %{HTTP_HOST} ^(.+)\.oomail\.org$ [NC]
RewriteRule ^(.*)$ /%1 [L]

Answer 2

It sounds like you want a reverse proxy. Fortunately, there's a flag to do this.

So you need to enable mod_proxy and add P to the RewriteRule flags.