Mail (Score 1)

There are two answers to this. One is Qmail which as long as you are familiar with this program and are willing to invest the technical time into it would give you the basics for mail. One draw back here is that you have no protection and would have to add an appliance due to the size of the network such as Symantec which would only increase cost and IT time. Second would be to again use Qmail and run ldap you could then proxy your mail through a scrubber lowering CPU usage and some maintenance time. The third and solution that I would highly suggest as being your best bet is to outsource this service to a subscription based provider that also includes mail protection i.e. Anti-virus, Anti-Spam, Anti-Spyware as well as the ability to control outgoing mail protecting sensitive company documents. There is only one Company that I know of that provides this complete mail with protection service and that is Sarron www.saron-corp.com.