I personally use Joomla 1.5.22 and mod_rewrite with nice links. But I must add additionally a redirection such as this:

RewriteRule ^mail /squirrelmail

Therefore if Someone makes its way into www.mypage.com/mail he'll be rerouted to www.mypage.com/squirrelmail

How you can update Joomla's .htaccess file to ensure that this to operate? For the time being, basically make use of this Rule, it shows a Joomla 404 Error

Inside your .htaccess find, and Following the following statement:

RewriteEngine On

ADD the next line

RewriteRule ^mail$ /squirrelmail [R=301,L]