How to reset the Auto complete in Outlook 2016 on Mac. 

Sometimes the Auto-complete might not work as expected. 

Quit Outlook and move the Recent Address folder from the following location to desktop: "\Users\<username>\Library\Group Containers\UBF8T346G9.Office\Outlook\Outlook 15 Profiles\<Profiles name>\Data\Recent Addresses" to any other location 

Note: Ensure to select the default Profile name of Outlook for <Profiles Name> in the above address.

Restart Outlook 2016 for Mac and the auto complete file will be recreated. 

Try sending some test emails.