Outlook for Mac 2011: Contacts showing question mark icon before contact name and doesn’t reflect the contacts correct details

Hi All,

Whenever someone sends me an email with some contacts on my address book CC'd, an orange question mark appear in front of the contact's name, and when I reply to that email the contacts with the question mark doesn't receive my reply. When I check the contacts with question mark by right-click open outlook contact option, I'm redirect to another contact in my address book.

This don't happen when I compose a new email. I've tried deleting the incorrect contact were it redirects when I open it but it doesn't help. Tried rebuilding database also since Outlook keeps prompting me to do it.

Outlook for Mac 2011 with SP2.