I am looking for some help in choosing software to run an e-mail service from. It must be scalable, support virus/spam filtering, anti-bombing measures, as well as all the usual aliases, autoresponsers and such.
I still havn't narrowed down a platform yet, but it will be Linux or Windows.
Money is not an obstacle, so feel free to suggest any software no matter how pricey (i won't be paying).
At the moment i am edging towards Windows software because programs like Postfix, Exim and others that run under linux require a lot of configuration an maintainance as well as not having any measures to prevent people from e-mail bombing the server (need to restrict messages/time).
Some of the windows solutions i have looked into are: Kerio, Merak, Workgroupmail, Mdaemon, Mailmax and Imail.
The service is going to be supporting around 20,000 users to start with.