When you send a message to a group, you will no longer receive a copy of the message in your inbox by default.
All groups created in Outlook include shared conversations, a SharePoint library, and a shared OneNote notebook, which are available to all members of that group. Group members can see any message sent to the group in the group conversations, and can continue the discussion directly from their inbox or in the group itself.
How can I see messages I send to the group in my inbox?
If you want to get a copy of messages you send to the group in your inbox follow these steps:
Sign into Outlook on the web in your browser.
Go to Settings , then choose View all Outlook settings.
In the Mail section, choose Groups from the navigation on the left.
Check the box for Send me a copy of email I send to a group.