Windows iis7 web & mail server settings & security check

We have a windows iis7 web server running a few hundred sites, as well as email through mailenable mail server. We need to have the server and email overlooked to make sure its running optimally as well as protected from hackers and spam attacks. As well, I would like to have DNS setup so that domains can point to the mail server instead of dong custom DNS settings on each domain. As well, setup user accounts with certain directories hidden. Initially, work to be done through team viewer and continued support in near future as work relation shows positive.