Use the /resetfolders switch to restore the missing folders at the default delivery location. To resolve this issue, reset or rename the Outlook folders by using Outlook for Windows. See the following screenshots: A working account The folder hierarchy in the mailbox may have become corrupted.įor example, in some cases, the Sent Items folder is converted into the Archive folder, and the icons that mark the two folders are incorrect. This issue occurs because Outlook 2016 for Mac can't locate and use the Sent Items folder. When you try to send email messages in Outlook 2016 for Mac, the email messages remain stuck in the Outbox folder, and you receive the following error message: Email messages are stuck in Outbox in Outlook 2016 for Mac