In CRM 2011, queues functionality is enhanced and changed as lot from CRM 4.0. You can read more about the changes in this article.
This current article is specific to behaviour with regarding to incoming email in to queue in CRM 2011. So if you received email in queue in CRM 2011 and if contact is not recognized by system automatically then it creates new contact automatically.
This is issue for one of customer because they did not want to end having lots of contacts created unnecessarily so we decided to turn off this feature for queues.
Following are steps to turn off this automatic feature in CRM 2011.
Step 1: Simply log on to CRM 2011 with administrative account (i.e. the account that was used to install CRM 2011 and CRM 2011 email router)
Step 2: go to File -> Options, this should open up Set Personal option page
Step 3: go to Email tab and un-tick option to automatically create records in CRM
Step 4: Click OK, Done!!
Hope this helps..