If you are a member of an O365 Group, you can learn more on the Microsoft Guides, and you can subscribe to group messages so they appear in your inbox. It is recommended that you double-check your O365 Groups so you don’t inadvertently miss important messages.
Once you have navigated to your Group within Outlook for Office 365, click on the gear icon shown below. Make sure the radio button next to "Receive all email and events'.
For more information, you can go to the Microsoft Guides: Get started with Office 365 Groups in Outlook