If you are experiencing failed sent mail due to malformed addresses in your AutoComplete or address book follow these instructions on how to clear your list and cache.
To remove entries from the AutoComplete cache specific entry , follow these steps:
- Open a new email message.
- Type the first few characters of the AutoComplete entry that you want to remove.
- When the entry appears in the list of suggested names, move your mouse pointer over the name until it becomes highlighted, but do not click the name.
- When the “X” icon appears next to the highlighted name, click X to remove the name from the list, or press the Delete key on the keyboard.
To disable AutoComplete and/or clear your AutoComplete list entirely, follow these steps:
- In Outlook 2010/2013/2016, click the File menu and select Options.
- In the Outlook Options window click the Mail tab.
- Scroll down to Send messages. Uncheck the Use Auto-Complete List to suggest names when typing in the To, Cc, and Bcc lines box.
To clear the AutoComplete list, simply click the Empty AutoComplete List button. You’ll see a confirmation window about clearing the AutoComplete list, click Yes.
Outlook AutoComplete should be completely disabled and any history that was in the auto-complete list should be completely erased (if you clicked the clear auto complete button).
More information about fixing nickname and AutoComplete lists can be found on Microsoft’s support site.