Microsoft's status website reported late Tuesday afternoon the service was "having problems accessing email," and warned Outlook and Hotmail users they "might not be able to see all your email messages," PC Magazine reported.
Users of Microsoft's Calendar and SkyDrive had been unable to access those services earlier Tuesday.
After around 17 hours of outage, Microsoft's status page reported the services back and running at 10:30 a.m. EDT Wednesday.
"Hotmail and Outlook.com experienced an outage that affected customers' access to their email. Fortunately the issue has been resolved and service is now restored to normal. We sincerely apologize for any inconvenience this caused our customers," Microsoft posted.
The new version of Outlook mail officially launched in mid-February after a six-month preview period, and Microsoft has been working to replace Hotmail users' accounts with Outlook accounts, though it will allow users of the older service to retain their current email addresses.