How do I fix disappearing emails and unsuccessful mailbox rebuilds?
Mail disappearing from certain mailboxes and rebuild not working?
[Re-Titled by Moderator]
Original Title: Rebuilding Mailbox not working
iMac 24″, macOS 26.6
Are those emails also missing on the webmail server of your provider? If so, you may have some Mail rules that move the emails to another location/mailbox. Try to use the search functionality to see if they reside elsewhere in Mail.