You may also encounter this message if you are behind a firewall. As a security measure, you can only access your MSN Hotmail account using the IP address with which you logged in. Using dynamic IP, the IP address stays the same throughout a session. Firewalls are designed to block transmissions of data sent out and to filter data packets to maintain security at a particular Internet site.
Many companies have firewalls between themselves and the rest of the Internet.
Firewalls can interfere with the sending and receiving of Hotmail messages or can cause unusual effects. Some America Online customers have problems retaining access to Hotmail after logging in. When AOL members launch their browsers, they are assigned an IP address from a pool of available addresses. During the course of a single Web session, a member may use any number of IP addresses as AOL dynamically reassigns addresses to balance load and improve response time. The Hotmail validation method works only for static IP addresses.