The list of names that Outlook uses is a combination of stored contacts, the company directory, and recent contacts. When you compose an email message and add people on the To, Cc, or Bcc line, Outlook suggests names as you type characters. This tool deletes all recent addresses instead of you having to manually delete addresses one at a time. The Reset Recent Addresses tool lets you reset recent addresses that Outlook stores. Exit the Default Mail Application tool.In the Default Mail Application dialog box, select, and then select Make Default.
This may require an hour or more, depending on the size of your Outlook profile. The Outlook Search Repair tool displays a "Reindexing, please wait" message while it works.