callback url 404

I have a plugin that calls another php file with a callback url in the parameters. When I try to go to the location I get a 404 b/c of the callback url.

https://examples.com/wp-content/plugins/example/redirect.php?callback=http%3A%2F%2Fexample.com%2Fwp-admin%2Foptions-general.php

If i remove the .com from the callback url, its ok.

is it a .htaccess problem? any thoughts?

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>