In Office 365, when someone sends a email to a distribution group they are a member of, they receive the message they sent in their inbox. It does not skip their email on the list, and sends the duplicate message. For example:
dave@contoso.com sends a message to group@contoso.com
dave@contoso.com receives the message that was sent to group@contoso.com*
Members of group@contoso.com also receive the message
*How do we prevent this step from happening?
Best Answer
All members of a Distribution group will receive messages addressed to the group. In hypothetical Dave's case, I would suggest an outlook rule to remove the item if it is a nuisance.
If the issue was a matter of controlling who can send to the Group, then it should be noted that there is a separate ACL for the ability to send mail to a group.
ReceivesMessagesFrom