I currently have Exchange 2007 in a single server environment. As instructed on parts of this forum, the permission group for the Default Hub Transport needed to include "Anonymous Users". I have noticed that emails can be sent from any of our "Authorized Domains" to any user under those domains without Authentication. For example, anyone could connect and send an email from support@company.com to user@company.com (or any other users in that domain) without any authentication.I'm wondering if there is any way to secure our "Authorized Domains" from anyone being able to send mail internally.Thanks,Ryan