Brightmail servers must run on the Solaris Operating System.
If Brightmail does spam and virus checking, MTA message throughput can be reduced by as much 50%. To keep up with MTA throughput, you may need two Brightmail servers for each MTA.
While SpamAssassin has the ability to perform different sorts of filtering on a user basis, it is unable to apply two different sets of filtering criteria to the same message at the same time. Thus, SpamAssassin only allows system-wide filtering. Customized filtering for individual users is not possible.