Exchange Anti-spam

Anti Spam for Exchange

Im currently using Antigen for my Anti Spam.However it is expensive so im planning to replace it.Do you have any recommended best anti spam for exchange which is not so pricey?

Do anti spam rules on Exchange have priority on outlook ones?

We have an antispam appliance and an Exchange server. For some users, some valid e-mails are put into the Spam folder on Outlook. We would like to white-list the IP of our appliance on Exchange in order to always tag those messages as "valid". We would like to know if this IP white-listing rule on...