Messaging Gateway

We recently received a Symantec Brightmail Gateway virtual appliance as well as Symantec Protection Suite SBE.  We are running a MS Small Business Server 2008 Premium edition.  My question is how the Mail Security provieded by SPS and Exchange 2007's own spam protection fits in.  Since we have the Brightmail acting as an in and outbound gateway, do we need to use Mail Security?  Should we also disable Exchange spam protection?

Normally I'd say "the more the marrier" but with SPS and soon Backup Exec SBE running on the server we are increasing the load quite a bit and would like to lessen the load wherever possible.  I would love if the Backup Exec media server could be offloaded onto another box, but from what I've read the SBE checks if it's being installed on Small Business Server.

I have also noticed that some spam has been delivered through the brightmail gateway and then rejected by Exchange based on content scanning.  I'm assuming this is due to Brightmail needing to build up it's database a little.  I have checked and the appliance is receiving all updates, so I know it isn't that. 

Thank you for any input anyone might have.

It is a good idea, especially if you have seen proof, to leave Exchange's spam detection running. Since Mail Security for Exchange's Premium Antispam is going to have the exact same rulesets as the appliance I would not recommend using that feature. I would stil recommend you have it installed though for virus scanning in case someone tries to send a file internally that is infected.

Thank you for the insight.  I was so focused on SPAM control and how internal to internal emails wouldn't be an issue that I forgot about virus emails.

I'm assuming I can disable content scanning in Mail Security, correct?