Summary: Outlook maintains a "nickname" list that is used by both the automatic name checking and the AutoCompletion features. The nickname list is automatically compiled as you send email messages to new recipients for the first time. If the nickname cache (memorized entry) becomes corrupt or the email account is disabled/enabled (i.e., the person leaves company then re-hired); Outlook may not be able to identify recipients and ultimately send you a "Delivery Failed" reply email. If this is the case, you will need to delete the cached entry.

Delete a single cached entry

  1. Open Outlook
  2. Outlook 2010/2013/2016: Click New Email.
  3. Type one or more letters of the recipient name or address; this will list any memorized (cached) entry in a drop-down list.
  4. Use the arrow keys on your keyboard to select the entry to be deleted. With the entry highlighted, press the DELETE key on your keyboard. This removes the entry from your autocompletion cache.
  5. Now that you have deleted the entry, click on "To" button again
  6. From the Address Book drop-down list select Global Address List [1] > type the desired name in the Search box [2] > Select the name and click the "To" button [3].

  7. Once you send this email the new contact will be added to your memorized (nickname cache) list in your Outlook address book.