It appears on Debian there is a /etc/amavisd.conf file that has a $max_servers variable that can be set to control the number of amavis processes that run on a server.
However, the file does not exist in Ubuntu and I believe the /etc/amavis/conf.d/50-user is the comparable file from Googling.
However, adding a "$max_servers = XXX;" to that file does not seem to have an impact on the number of amavis processes running. I am doing a "sudo /etc/init.d/amavis restart" after making any changes to the configs...
How do I change the amavis process limit in Ubuntu 13.04?