Looking it up post mortem it doesn't appear that it was several days, but it sure felt like it at the time. It was over 12 hours. There were significant outages on March 12th-13th [1], Feb 25th [2], and Feb 1st [3].
Thank you for providing the sources. Looks like you were right (except the few days part). It only affect a subset of users which explains why it went unnoticed for me. May have been related to the transition of Hotmail accounts but regardless if it keeps happening on a regular basis, I may have to find another provider.
[1] http://www.businessinsider.com/microsoft-forced-to-apologize...
[2] http://www.neowin.net/news/microsoft-outlookcom-down-for-som...
[3] http://gigaom.com/2013/02/01/microsoft-office-365-hits-potho...