If messages appear to be missing
If messages seem to be missing from mailboxes, try these suggestions.
If you use more than one email account in Mail, make sure you’re looking at messages for the correct account.
If you sorted messages, they may be in the list but not in the order you expect.
Check the account’s Recovered Messages mailbox, if available in the Mail sidebar.
Quit Mail, then reopen it.
If the problem persists, you may need to rebuild a mailbox.