We need to be able to disable autocomplete like we can (and do) via GPO on Outlook for Windows. Many people are erroneously sending mail to "no-reply@sharepoint.com" or other such addresses because the displayname they are looking for is being auto-completed based on a received note that is not meant to be replied to. There is an equivalent request on the consumer uservoice here: https://outlook.uservoice.com/forums/293343-outlook-for-mac/suggestions/18770335-have-the-ability-to-disable-autocomplete-feature-f