When using Office 365 Groups in Outlook, all conversations, replies to posts, and calendar events are delivered to the group inbox. But copies of them can also be delivered selectively to the personal inboxes of group members. If you work primarily out of your personal inbox, having all group items delivered there is convenient, particularly if you don't want to miss anything. But if you'd prefer to limit what goes to your personal inbox, you can do so by customizing the group subscription.
What are my group subscription options?
Group subscription settings are similar to inbox rules in that you specify where each type of group message gets copied to your personal inbox. The difference is that the group messages going to your personal inbox are copies of what goes to the group inbox. You can specify how to distribute conversations, replies, and calendar events based on how you'd like to keep track of a group. This setting can be customized on a per-group basis. The following image shows the menu option used to control the flow of group messages in your inbox.
To customize how you receive group messages
In Outlook on the web select a group that you're a member of.
In the group header, select the down arrow (v) next to Joined.
Select Subscribe to this group by email.
This option copies all conversations and events from this group to your inbox. If you want to instead reduce the flow of group email to your inbox and are already subscribed to this group, select Unsubscribe from email for this group. Selecting this option results in copying only replies to your posts, messages where you're mentioned, and group events in your inbox.
Repeat for each group.