gmail & bulk forwarding Options

[batman]

Ok, here's the thing. I have a form on my website that forwards form submissions to one email and I recently redirected it to a new email address.

However, I still have 300 submissions sitting in the old email and I was wondering if there was a way to bulk transfer all of those old emails to the new email address.

I tried filtering, but that only works with incoming mail and not old mail. I also don't want to do any pop forwarding because I ONLY want the form submissions to be sent to the new email address.

Is there a quick and easy way to do this?