Last Updated Aug 16, 2010 6:19 PM EDT
Here's an unexpected goodie: Outlook 2010 solves this problem by remembering every e-mail address you've ever interacted with in a feature called Suggested Contacts. I've noticed this feature before, but never really understood what it did until I read an explanation at the Microsoft Outlook blog.
Here's how it works: Click Contacts and then, in the nav pane, click Suggested Contacts. Now just type some part of the address -- like the domain or the recipient's name -- in the search box on the right. Since Outlook tracks every e-mail address, like, ever, here in Suggested Contacts, you should see the result you're looking for.
Now, just click E-mail in the ribbon and you're good to go.