Microsoft said Wednesday that its Hotmail and Outlook services were experiencing problems that may prevent users from seeing all of their messages.

The company first posted messages about the outage on Tuesday night, though it has yet to provide specifics about what’s causing the problem. In its latest update, the company said simply that the problem was taking “longer than we hoped” to fix.

No other services, such as SkyDrive or Messenger, appear to be affected by the issue.

Microsoft is working to replace Hotmail users’ accounts with Outlook accounts, though it will allow users of the older service to hang on to their current e-mail addresses. All users, however, will see a new layout for their e-mail accounts, as well as features from the new Outlook service such as the ability to move, delete or mark multiple inbox messages at once.

The company said last month that it expects to have all Hotmail users migrated to its new platform by the summer, though Hotmail users can already elect to change to the new format.

Microsoft is setting up Outlook as a competitor to Google’s Gmail service, having launched an aggressive campaign going after its archrival for serving ads based on the contents of users’ e-mails. Both companies advertise on their e-mail products, but Google uses algorithms to scan through users’ mail to show relevant ads, while Microsoft bases its advertisements on information that users provide to the company and their search histories.

The new version of Outlook mail officially launched in mid-February after a six-month preview period in which it grew to 60 million active users.

Microsoft said Tuesday morning that it will provide users with further updates on the disruptions mid-afternoon.

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