In Windows Exchange 2003, what I used to do is installed SMTP service on a dedicated server, then installed the Anti Spam to filter all the spam emails.
In Exchange 2010, the roles have been separated which means you have the option to combine all roles and install them in single server or separate each role by installing a particular role on a particular server.
What is the best practice particularly when installing Anti Spam application (e.g. Trend Micro Spam Mail). Would you install it where Exchange server is installed, let say all roles were not separated but rather all installed in one server or should you separate the HUB transport to a particular server, then install the Anti Spam?
Appreciate any help.