Sending, receiving, and organizing email in Outlook.com
Hi, BRADFORD PEARCE
This appears to be a recent Outlook interface change rather than a problem with your Office installation. The message checkboxes are now hidden until selection mode is enabled, and there is currently no setting to keep them permanently visible.
Here are some suggestions you can try:
In Outlook on the web, open Junk Email and look beside the folder name for a small square Select icon. Select it to display the checkboxes, then use the top checkbox to select all messages.
If the icon is also missing, place the pointer inside the message list and press Ctrl+A, then press Delete. This shortcut has worked for the same recent issue.
To remove everything without selecting messages individually, right-click Junk Email and choose Empty folder. In Outlook on the web, you may instead see Delete all at the top.
Since the control is missing in both Outlook and OWA, reinstalling Office is unlikely to help. If none of these options appears, use Help > Feedback in OWA to report the interface problem.