Previously I wrote an article, located here, about the NK2 file on Windows that stores the email addresses you type into the “To Field” when sending emails. The NK2 file stores the history of what you type or paste into the To field so it can auto complete for you in the future. This is a great feature however deleting old entries is not always the easiest and that makes it a bit unfortunate. You can typically turn off auto complete however you could also modify the files that store the contact cache that is used for auto complete. Follow the directions below to locate email addresses stored in the To Field Outlook for Mac cache to either modify or delete.