That IP Address is used by calibre to collect anonymous usage statistics, it redirects to: https://calibre-ebook.com/dynamic/calibre-usage
There doesn't appear to be a method to configure calibre to not send this information, so you will have to block it in your firewall.
In windows 7 you can add a rule to the firewall to block a specific IP address pretty easily:
a. Click Start
b. Type "firewall" and click on "Windows Firewall with Advanced Security" that will appear under "Programs."
c. Select "Outbound Rules" on the left panel of the firewall window.
d. Right-click and choose "New Rule" from the pop-up menu.
e. Select the radio button "Custom" and click "Next."
f. Select the radio button "All Programs" and click "Next." Then click "Next" again.
g. Select the radio button "These IP addresses" in the field "Remote IP addresses. Click "Add" and type the IP address you wish to block in the field. Click "OK" and then "Next."
h. Select "Block the connection" and click "Next."
i. Type a descriptive name for this Windows firewall rule. Click "Next" and then "Finish" to create the rule that blocks the IP address.
Instructions pulled from: from http://answers.microsoft.com/en-us/windows/forum/windows_7-security/how-do-i-block-outbound-and-inbound-specific-ip/d42c58d0-2693-4a10-a4e4-331b7d041036