[http://support.microsoft.com/library/images/support/cn/way-windows-selected.png]

Considerations for Lync Online when you change an Office 365 user ID
http://support.microsoft.com/kb/2537764/en-us?sd=rss&spid=15834&utm_source=twitterfeed&utm_medium=twitter
Describes how sign-in addresses and user IDs are managed in Microsoft Lync Online.