How to delete the unwanted e-mail id from your local contact list cache of Outlook?

Microsoft Outlook has a feature called Email Address Auto Complete cache. When you start typing an email address into the TO:, CC: or BCC: field, Outlook will display a list of matching email addresses from the outlook auto-complete cache. 

Outlook always preserve the local cache of all the contacts that have been used so far. When you start typing characters at the address field, outlook pop-up the relevant contacts from the cache list.

In case if you find the contacts which are not required, incorrect, outdated, you may click on the cross button (refer the screenshot) against this contact. Now, that contact is deleted from your local cache list & will not pop-up next time. This will help you to avoid sending emails to incorrect  - unwanted email address.