This Collaborator Portal runs on Google Sites so that we can easily and securely control access to it. To request access you must use an email address with an associated Google account. We need to keep access. This does not have to be a G-mail address. You can create a Google account associated with any email address. Just register for a Google account associated with your existing email address. This doesn't affect how you use an existing email address. It just allows you to sign into Google apps using that address.