Miscellaneous topics that do not fit into specific categories.
When emails disappear without being deleted, the most common causes are a view or sync change, Focused Inbox being toggled, a filter being applied, or an account sync issue. Sometimes messages are also moved automatically by a rule or temporarily hidden due to a refresh error. I recommend first checking Other, Archive, Junk, and Deleted Items, then turning filters off and refreshing the inbox. You can also try signing out and back in to force a sync. https://support.microsoft.com/en-us/office/email-is-missing-from-your-outlook-com-inbox-c70b4a9a-caa5-4e8c-a88a-3372215af25e
If the emails were moved by mistake, you can often recover them, https://support.microsoft.com/en-us/office/recover-and-restore-deleted-items-in-outlook-49e81f3c-c8f4-4426-a0b9-c0fd751d48ce.
Are you using Outlook.com, Outlook desktop, or a mobile app? And did this happen on one device or across all devices at the same time?