Hi Charles,
I understand that you couldn’t see the recent addresses in the dropdown list of address typing box when you type an email address recently used.
Could you confirm the following information:
1. Did this issue occur suddenly?
2. Is there someone else in your organization encounter this issue?
3. Do the recent contacts show up when you type an email address in OWA?
4. Could you configured your account on another computer to see if it works?
We suggest rebuild the identity on your Mac and try again. To rebuild the identity, please refer to http://support.microsoft.com/kb/2360509.
Thanks,
Lee Li