Outlook 2010 does you a huge favor, even if you’re unaware of it. Everytime you email someone that isn’t one of your saved contacts, Outlook saves them just in case you need to use them again someday. This is a much better way to find an address of someone that you emailed months ago but neglected to save them as a contact.
1. Open Outlook.
2. Go to the bottom-right of the application and click the Contacts button.
3. Under My Contacts, click Suggested Contacts.
4. In the middle pane, you will see that Outlook has created a contact card for each person that you’ve emailed.
You can drag the desired card to either the Contacts object under My Contacts or down to the Contacts button in the lower-right corner to move the unsaved contact to your Contacts list.