Hello Clements,
Welcome to Apple Support Communities!
If we understand your post correctly, certain emails on your Mac are not getting indexed. We'd like to help!
"If you don’t get expected results when you search for email messages in the Mail app
on your Mac, try these suggestions.
- If one or more mailboxes are selected in the Mail sidebar or the Favorites bar, Mail searches only those mailboxes. To search all mailboxes, click All Mailboxes in the sidebar or All in the Favorites Bar.
- Mail may not be looking in the Trash or Junk mailboxes, or searching encrypted messages. To include them when searching all mailboxes, choose Mail > Preferences, click General, then select the options.
- You may need to sync the mailboxes on your Mac with those on the mail server. Choose Mailbox > Synchronize > [account].
- Mail may be excluded from Spotlight searching. To check, choose Apple menu
> System Preferences, click Spotlight
, then click Search Results. If the Mail & Messages checkbox isn’t already selected, select it. - The Mail folder (located in your home Library folder) may be excluded from Spotlight searching. To check, choose Apple menu > System Preferences, click Spotlight, then click Privacy. If Mail is listed, select it, then click the Remove button
."
If searching doesn’t find the right emails in Mail on Mac
We also recommend checking out this article for help with searching mail on your Mac: Search for emails in Mail on Mac
This article has steps to rebuild your Mailbox: Rebuild mailboxes in Mail on Mac
"You may need to rebuild a mailbox to update the list of messages it contains. For example, if messages appear to be missing or garbled, or if you can’t find all relevant messages when you search using the Entire Message search option."
Let us know if you have any questions.
Thank you for using Apple Support Communities.
Take care!