If someone leaves the company and then comes back after a period of time, you may receive a non-delivery report when trying to email them.
This is a common issue when someone leaves the organization and returns. It is related to the Outlook address auto-complete cache.
- Inside a new Outlook email, type the email address in the To: field you wish to clear from the cache until Outlook displays it
- Press the down arrow key to select the email address and hit the delete button.
- All Done. That entry should now be gone from the Outlook Auto Complete cache
Then add recipients name from the Address Book (or just type it in).