Actually my problem is that "Can we identify the contacts that are being imported from outlook into sales-force" is there any sign that helps the user to be clear that "Oh, this contact is from outlook.." and "Ah, This is a sales-force Contact.." kind of thing. Like a checked check-box for outlook contact and unchecked check-box for sales-force contact. Thanks.
You could set up a custom Outlook field sync to a custom Salesforce field. See Editing Your Salesforce for Outlook Field Mappings for more information on mapping custom fields. It will still take some effort on part of the user to make sure that they're filling out the custom field/setting a known value to report on. I'm pretty sure you could write a macro to automatically populate the correct value. It will take some moderate effort to make this work, however.