Mail shows a number next to the Junk mailbox to indicate how many unread
messages it contains. Sometimes you’ll see the number, but when you click on the
mailbox to see its contents you’ll see either no messages or no unread messages.
This may be because:
- The unread messages are actually in a second mailbox, inside the
Junk mailbox. If there’s a triangle to the left of the mailbox icon,
click to make it point down. This will reveal any mailboxes inside and allow
you to access their contents.
- Mail’s database is damaged so that the numeric display is out of sync with
the actual mail that’s stored on your Mac and/or your server. You can fix
this by rebuilding Apple Mail’s database.