Yahoo! Messenger is an application that enables users to communicate over the Internet in real time. It allows users to send instant messages via Yahoo! or Windows Live Messenger. Instant messages may be transmitted to and from multiple users through a conference (IM Conferencing), users from other networks (Reuters Messaging, Lotus Sametime) or via SMS (Text Messaging) without charge. Files and photos from a user's desktop or Flicker account may also be shared with a 2GB limit. Calls may also be made from one PC to another. Its design alerts users to newly arrived Yahoo! Mail, allows users to follow up on each other with the Buzz feature, and sends messages to the user’s mobile phone upon signing out or through voicemail. It allows users to search the Web from the Messenger UI (User Interface), search their contacts or address books. Yahoo! Messenger may also be accessed via the Yahoo!Mail, website and has versions for Windows, Mac and iPhone systems.