Usage of Piwik and Data Mining (Campaign, IP and User)


I recently installed Piwik on some sites to have more control over statistics and, especially, to be able to make good use of the informations stored.

Piwik is powerful, i can add Custom Variables, track newsletter’s campaign creating new Campaigns, etc… now there is my problem: how can I make a good use of all this informations?
By example, i create a newsletter Campaign. A week after I want to know if that newsletter was usefull so I want to search inside the visitor log to know if someone entered my site by clicking the newsletter.
How can i do that?

Moreover, all those newsletter was sent to subscribed user so, how can I associate the visit to the site with the user?

Or even, how can i filter all the visits in Visitor’s log by IP addres? For example, I know that a company has a static IP so i want to know if someone from that company enetered my site.

I hope this message is clear enough (my english skill isn’t high),