Do you send out email campaigns regularly? Are you able to track the effectiveness of your email campaigns?
If your answer is 'Yes' for the first question and 'No' for the second question.. then you would find this post helpful.
Tagging email campaigns links would supply you with the statistics of visitors activities after they enter you web pages by following the link in your email campaign. Campaign tags can be created very easily using Google's URL builder tool and tracking the visitor stats can be done using Google analytics, a free and powerful web analytics tool.
Understand your email campaign prospects behavior using Google Analytics.
Using email marketing solutions like Campaign Monitor, MailChimp, VerticalResponse and AWeber will automatically tag your campaign links.