500 Server Error that should been 404 server errors

[Mopar1973Man]

This is something you end user wouldn't normal see on your end but I've been trying to figure out for a little while. I've been using Mod Rewrite commands on the server to simplify the URL or web address so it user friendly also Google friendly. Well Google has been constantly complaining about old links from long ago (3-4 years ago) when I was still using PHPbb 3.0.4 software. Well Google continues testing those links and getting 500 error code for the page. Finally I took the time kick the server logs in to gear and looked it over. Come to find out I've been missing the code to redirect 404 pages somewhere. Now they redirect back to forum index page. So I added to my .htaccess this line below and no more 500 error codes...

# 404 FilterRewriteRule ^(.*)$ - [R=404,L]

Then I ran back over to Google and cleared out all the listing of 500 error codes and the links. Now let Google wander the site now and see if it can find any problem now...