How big is Hotmail?

Huge. Here is some data from a PDC Hotmail presentation:

~200 million active users

3.3 billion inbound emails a day

  • 1.5 billion blocked at the router
  • 1.0 billion deleted as spam (never hits the user's mailbox)
  • 0.5 billion sent to the junk folder

Over 100 million messages sent a day

80 - 100 milllion logins per day

5000 peak logins per second

But the most interesting part in this PPT is the new FrontEnd design. It is based on the Atlas framework. The client code (Javascript  - in the browser) is able to call into front-end components (written in C#). The requirements for the protocol are interesting: minimize the data on wire, purely asynchronous processing at the server side. All this combined with an OOP component framework.