This plugin do what is says,
Only the 404 error is still not solved.
When you have the wordpress in a subdirectory and someone submits an email adres, you get the error 404.html in the content frame.
Even when you change to get_site_url() like FAQ says.
So if someone have the solution to that problem than i give it 5 stars.
Now i give it 3 stars because it is stil doing what is says.