Mailman
In moving from a cPanel host to a VPS, I decided to setup Mailman. Mailman isn't my favorite program, as I don't like it's strange way of handling passwords, and ugly interface, but it does get the job done. Mailman is secure and well documented. After running out of memory twice on my VPS, I decided to disable Mailman. Unfortunately, Mailman keeps all these qrunner processes running. I would prefer for Mailman to not be in memory except when it's doing work. Postfix could easily launch it for incoming mails, and it could use cron for daily batching. Turning off Mailman had a significant affect on my server's memory:
