DirectoryIndex index.php
RewriteEngine on
#RewriteBase /
RewriteCond %{HTTP_HOST} ^(.*)$ [NC]
RewriteRule ^/(.*)$ http://%1/redirect.php?key=$1 [R=301,L]
# Ниже строка
#RewriteRule ^/(.*)$ /redirect.php?key=$1 [R=301,L]