The screenshots in these instructions use Outlook 2013. The same process can be applied to Outlook 2010 as well.
If you would like Outlook to automatically accept any meeting invitations you may get, follow these instructions.
With Outlook open, click on File from the tabs at the top.
Select Options from the menu on the left.
In the window that appears, select Calendar from the options on the left.
Scroll to the bottom of the window and click on Auto Accept/Decline in the "Automatic accept or decline" section.
Check the option Automatically accept meeting requests and remove canceled meetings. This adjusts your settings so Outlook automatically accepts all meeting requests (and removes meetings that have been canceled). The person who requested the meeting will receive an email from you accepting his or her request.
Once this option is checked, the options below it become available as well. Checking Automatically decline meeting requests that conflict with an existing appointment or meeting will adjust your settings so Outlook will automatically decline a meeting request that overlaps with another meeting on your calendar. The person who requested the meeting will receive an email from you declining his or her request.