For some reason, people think that hidden services are safer than clearnet sites. Hidden services are designed to protect the server. As a Tor user, you have the same level of anonymity, whether you are browsing a hidden service or a clearnet site. There are a few advantages to hidden services, such as LE doesn't know where they are located or who to subpoena. Using a hidden service can protect you against accidentally connecting to a site in a way that reveals your IP (for example, configuring an IRC client to use a hidden service is safer, because if you turn off the proxy settings it will fail instead of connecting you to the IRC server with your real IP address). However, in general, you have the same amount of anonymity with clearnet site as with a hidden service -- there are three proxies between you and the IP address the server sees. So the short answer is, if you use Tor correctly (TorBrowser in the default configuration), your real IP won't be leaked to Hotmail. However, there are lots of things you can do to accidentally deanonymize yourself, even when Tor works as intended. Read this article about how the FBI found a guy who was using Tor because he revealed 4 or 5 pieces of information about himself: http://arstechnica.com/tech-policy/2012/03/stakeout-how-the-fbi-tracked-and-busted-a-chicago-anon/ So don't reveal personal info.