To expand a bit on the distinction:

- Symantec Mail Security for Microsoft Exchange installs directly on your exchange server.  It provides the core Symantec AV Engine, as well as the Brightmail Antispam Engine and flexible content filtering policies.  For an SMB customer, this is absolutely a recommended solution for email security, and as JDavis above suggests, there is a very robust roadmap and support plan for this product.

- Symantec Brightmail Gateway is a gateway product that sits in front of your Exchange server.  It can be deployed either as a physical or as a virtual appliance.  As a gateway device, it requires independent hardware from your Exchange server, but it has the benefit of doing all of the filtering before the email hits your internal network.  If you are experiencing any scalability issues with Exchange, the gateway model is a much more efficient way to protect a larger scale Exchange deployment.  Brightmail Gateway also includes additional functionality, such as Adaptive Reputation Management which can filter over 90% of spam at the connection level.  The primary benefit of this filtering is for scalablity and performance, so again it may be less important for an SMB environment.  If you are interested in a gateway product, take a look at Symantec Brightmail Gateway Small Business Edition, which is specifically designed for SMB customers.

- Symantec Brightmail Message Filter is a software-based spam filtering solution.  Earlier versions were called Symantec Brightmail AntiSpam, and some SMB customers use that product for spam filtering.  Brightmail Message Filter is really focused on deployment flexibility and very high performance filtering for the largest and most demanding environments, such as service providers.  For an SMB customer today, I would recommend Symantec Mail Security for Microsoft Exchange as the best solution, unless you want a gateway product, in which case I would recommend Symantec Brightmail Gateway Small Business Edition.

Hi BSharpe,

I recommend SMSMSE (also known as SIFMSMSE) for the SBS.  I've had it installed on my Win2008 Small Business Server for a while now, as well as SEP Small Business Edition.  It's working well enough in all my experience.  

Here's an article that may be of interest: Best Practices document for Symantec Mail Security for Microsoft Exchange on Microsoft Small Business Server

Thanks and best regards,

Mick

My company used to run Mail Security for SMTP in front of our Exchange and it worked fine.
However, it was suggested to us that we should try the Brightmail Gateway. We purchased the Brightmail gateway 300 appliance in virtual for deployment.

In 36 hours we saw a significant increase in blocked spam over the Mail Security. The Brightmail is very robust and a bit tricky to get configured at first, but I have to say that we have not had any major issues since installation. It has better features over mail security and some more control as well.

It would be a great investment for any small business that needs tough security.