First I do not work for MS.
MS is aware of the problem and working on it. It May have something to do with the migration of all users to the Outlook Preview>and the newly released Outlook mail formats who do no support "groups". They do support contact lists which is essentially
the same thing.
Microsoft has not announced an ETA for the fix
CONTENT COURTESY OF MY PARTNER JMH3143
There is in progress an update to Outlook.com that lets you make the most of the moments that matter to you—featuring a refined inbox, an upgraded calendar and more.
The update being rolled out in Preview and now is being released to the public and is called Outlook Mail, is the first of many innovations coming as Microsoft
upgrades Outlook.com to a new Office 365-based infrastructure.
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There is no returning to the old system
**New ways to get more done in Outlook.com**
Welcome to Outlook on the web
**Outlook UserVoice**, is an open forum for you to share feedback, recommend features, and vote for the ideas you like best.
Joining the conversation in the updated web experience is easy—just click Feedback under the Gear icon and you can make your suggestion without leaving your inbox.
If you’d like to see and vote on other ideas, you can always visit Outlook.UserVoice.com and sign-in with your Microsoft account.