The problem occurred globally, and Microsoft said that over 17,000 customers were affected in total. The issue was caused by mailbox load balancing between servers, which evidently went very wrong.
Microsoft’s Chris Jones issued the apology on the Inside Windows Live blog. He wrote: “We identified the root cause and restored mail to the impacted accounts as of January 2nd. As with all incidents like this, we will fully investigate the cause and will take steps to prevent this from happening again.”
“We’re very sorry for the inconvenience this may have caused to you, our customers and partners.”
However, some users are still posting that their emails haven’t been restored yet. If you’re one of those unlucky ones, then your best bet is to contact Microsoft and let them know (a bit of praying probably wouldn’t go amiss, too).