From Windows Live Blog:
Beginning today, Hotmail is providing you with the option to enhance the security of your entire Hotmail session with HTTPS data encryption (via secure socket layers, or SSL), which is currently used to help secure your Hotmail sign-in. Today's update joins a series of other recent security updates, with which Hotmail offers advanced security safeguards to help protect your email account from hijackers and fraud.
Also starting today, SkyDrive, Photos, Docs, and Devices pages all automatically use SSL encryption, transferring all their data over HTTPS. By using a connection with advanced security features, you can be even more confident that your account is safer from hijackers, and your private information is less likely to fall into someone else's hands.
To enable HTTPS for your Hotmail inbox, calendar, and contacts, go to account.live.com/ManageSSL. Once you enable this feature, all of your future connections to Hotmail will be delivered over SSL.
Some connections to Hotmail won't be available if you turn on HTTPS, including:
Outlook Hotmail Connector
Windows Live Mail
The Windows Live application for Windows Mobile (version 6.5 and earlier) and Symbian