Like Microsoft Entourage for Mac 2008, Outlook 2016 for Mac and Outlook for Mac 2011 are intended to be purely locally cached mail clients. Changing the location or using a mail identity that is located on an external hard disk or a network is not supported. In Outlook, click Help > Check For Updates. If an update is found, download and install it. Restart Outlook. If the problem continues, click Help > Contact Support.
Many clients have the ability to remember what addresses you have sent messages to, this is known as your auto-complete list. Sometimes you may enter the wrong address for a recipient or the recipient changes their address. The steps below will guide you through the process of either removing an address from this list or clearing the entire list. Note: If you are experiencing an error indicating that no match is found or that the message cannot be sent because one of the addresses is invalid, clearing your Auto-Complete list could solve the issue. Important: Your auto-complete list is not backed up.
If you delete an entry or remove all entries from the auto-complete list, there is no way to recover this. • Outlook on the web • Removing an address from your auto-complete list • In Outlook on the web, click the New button to start composing a new email. • In the To: field, start typing an email address. • Using the up and down arrows on your keyboard, select the email address you would like to remove from the suggested contacts list. Press the Delete key on your keyboard.
Clearing out the entire auto-complete list Note: In order to clear the entire Suggested Contact list, you will need to use Outlook on the web Light. For further information regarding Outlook on the web Light please refer to the following document: • In Outlook on the web Light click the Options button located in the top right. Click Messaging in the left-hand pane. • Under 'E-Mail Name Resolution' click Clear Most Recent Recipients list. • Outlook 2016 for Windows • Removing an address from your auto-complete list • Open Outlook. • Click the Mail tab on the bottom of the screen so you are viewing your mailbox. • Click New Email.
• In the new e-mail window, start typing the address you want to remove in the To: field. When it appears, click the X button next to the address.
Note: If you do not have the ability to delete an entry, then either the address is coming from the directory or your personal contacts. 
You cannot delete the entries from the directory but you can delete/update entries within your personal contacts (e.g.
Clearing out the entire auto-complete list • Open Outlook. • Click the File tab at the top of the screen. • Click Options. • In the 'Outlook Options' window, click the Mail tab in the left hand pane.
• Scroll down to 'Send Messages' and click the Empty Auto-Complete List button. • Outlook 2016 for Mac • Removing an address from your auto-complete list • Open Outlook. • Click the New Email button. • In the new e-mail window, start typing the address you want to remove in the To: field. When it appears, click the X button next to the address. Note: If you do not have the ability to delete an entry, then either the address is coming from the directory or your personal contacts.