If you are setting up a new virtual server (eg. on Rackspace / any VPS provider), the first thing you will want to do after creating the server, is to check the IP address you are assigned against known blacklists. If you find that your new IP address is on one of these lists, rather than try and remove the IP from the blacklists, it might be quicker to create a new virtual server (which will assign a new IP address), and then delete the old one.
Even if you can remove the IP from blacklists, there is usually a reason for the IP being blacklists. You may find that you get excessive connection attempts from bots to common proxy ports, and even SMTP connections. These connection attempts may be almost impossible to stop until the bots have been disabled. These requests may not cause excessive traffic, but it can be annoying.
You can check to see if your IP address is on a black list on sites such as http://mxtoolbox.com/blacklists.aspx
If your virtual server provider allows you to change IP addresses, that’s the best option, but if not, and if this is the first thing you check after the server is set up, its easy enough to remove the server, and create a new one before you start configuring it.