Are you using Windows Live Messenger in a corporate intranet, and experiencing the error code 80072ef3 when trying to sign in?
Changed port configurations in the latest version of Windows Live Messenger (2009) cause this issue
Solution 1: Add Messenger servers to exception list
Click Start, Control Panel, Internet options.
Switch to the Zones tab.
Mark the entry Trusted sites, and click the Sites… button.
Add the following entry to the list of trusted sites:
Click OK, and switch to the Connections tab.
Click the LAN settings button. If the Advanced button is active, click it and add *.contacts.msn.com to the Exceptions list.
Click OK to close the dialogs.
Retry to sign in to Messenger.