Select Settings → Mail → Message list → Layout → Checkboxes; the checkbox control is now under Message list, rather than the general Mail → Layout page you checked.
- Open Outlook.com.
- Select Settings (gear icon). If the full settings page appears, the path may begin with File → Settings.
- Open Mail → Message list.
- Expand Layout.
- Under How do you want messages to appear in the message list?, select Checkboxes.
This restores persistent checkboxes beside messages for bulk deletion, moving, and other actions. Users affected by the same Outlook.com interface change confirmed this path restores them.^1^
If “Checkboxes” is not available yet
The new selector may not have reached every account. Look specifically for Show sender images—not “Show Sender Message”—under:
Settings/File → Settings → Mail → Message list → Layout
Turn Show sender images off. In the earlier version of this interface, disabling sender images restores persistent checkboxes.^1^
Temporary selection option
If available, select the Select icon—a box at the right side of the folder name above the message list. This temporarily displays the checkboxes so multiple messages can be selected.^2^
The distinction is:
- Checkboxes setting: keeps checkboxes visible.
- Show sender images off: rollout-dependent fallback that keeps them visible.
- Select icon: exposes them temporarily for the current bulk operation.
References
- Check boxes have disappeared - Microsoft Q&A
- Check boxes have disappeared - Microsoft Q&A