With Click, you can track emails you send from Microsoft Outlook. This is nice if you are sending something important and you want to know if the recipient clicked it and where they went on your site after. To do this simply add a link in your email (using control 'K' is a shortcut) and then add the parameter _clde=email to the end of the link. Here is an example of what your link should look like:
http://www.clickdimensions.com/tour/?_clde=bob@fakecompany123.com
After the recipient clicks your link, all his or her browsing on your site will be tracked; even if they've never previously been to the site. Of course, the email you include in the link will already need to be in your environment in any of the three Contact or Account email fields. You must also have the tracking script on your website - see how to set that up here.
By the way, this link format works regardless of where it comes from. You could message the link to the person, embed it in a PDF or other document and it would also work. But, remember, the link is specific to the person whose email is in it.