In May 2015, Microsoft announced a big overhaul was coming to its Outlook.com free mail service. The new look Outlook.com looked a lot closer to the Outlook Web Access component in Exchange. It had Exchange features like the Clutter folder for handling all those e-mails that aren't quite spam but aren't quite important, pinned and flagged mail, new calendar views, and a better mobile interface that supports swipe-based gestures. In February 2016, this new experience was announced as being out of beta, and Microsoft rolled it out immediately to new users in North America. Everyone else was scheduled to be upgraded by the end of summer.

It looks like that's not the plan any more. The upgrade has been partially performed, and some users have been upgraded while others have not. A new error message (spotted by Twitter user gwydionjhr) suggests that those who don't have the update by now won't get it for quite a while. While attempting to share calendars, users have noticed that sharing between non-upgraded and upgraded users isn't possible, and this situation apparently won't be remedied until the first half of 2017.

It's not clear what the hold-up is or why the roll-out is taking longer than expected. The rollout is a big one behind the scenes, with Microsoft saying that the new system uses "Office 365-based infrastructure" and that there are hundreds of millions of accounts to migrate. Certainly the scale of what Microsoft is doing is certainly significant, but the delays are also frustrating, especially for anyone wanting to share calendars.

Update: Microsoft has now told Mary Jo Foley that the 2017 date is in error and that 90 percent of accounts have been migrated. Some users, however, will take "additional time" to migrate due to their use of features such as shared calendars.