If emails appear to be missing in Mail on Mac
If messages seem to be missing from mailboxes in the Mail app on your Mac, 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.
If the missing emails are from a specific person or group, check whether you blocked messages from them.
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.
If you set up Time Machine to back up files on your Mac, you can use the backups to restore content that Mail downloaded (based on options set in Mail and on your Mac). See Restore items backed up with Time Machine.