9. Outsource Your Spam/Junk Mail Filtering
It is true that money is at the root of anything evil. Money is at the root of spam and junk mail. Spammers send millions of email, and even if only 1% of receivers click one of their spam links, they can make significant money! Spammers also send emails to infect people that receive them with a program that will turn the computer into a spam zombie--i.e. a spam email sender.
As a business, when you acquire your domain, you likely also acquired basic email services which allows for receipt of email into your domain, like email@example.com. Most of these email services are pretty basic--i.e. your mail boxes receive all emails, regardless of whether it is legitimate or plain junk mail.
With the magnitude of junk email floating out there, you will definitely need a spam/junk filter for inbound and outbound email. In general inbound junk/spam email constitutes around 80% of all emails received by a typical organization. Without any kind of filter, a business would be overly burdened by unnecessary email. This can impact productivity, as well as use up space.
If any of your computers become a zombie for spammers, your organization could also become a source of spam. When that happens, your domain will quickly get shut down by major ISPs. As such, none of your emails will reach their intended recipients. The only fix for this kind of damage is to contact each ISP and let them know what happened and promise them that you've removed the offending computer from your network.
There is one easy solution for this (and it is with minimal headache)--outsource email filtering for both inbound and outbound traffic. Google provides such a service--called Postini. Pricing is very competitive, with basic message security costing only $12/yr per user.