Reroute meeting accepts/declines to another folder, and review them periodically. Then, just delete them. Outlook tracks meeting accepts for you without the message. Here’s how.
From Rules in Outlook, choose Create Rule and Advanced Options. Check the box for “uses the form name form.” Then click the link in the Step 2 section. Change the forms group to Application Forms in the dropdown on the left, and locate Accept Meeting Response and Decline Meeting Response. Add to Selected Forms and choose the target folder.