Mail for mac does not find e-mails of the last month
If you don’t get expected results when you search for email messages in the Mail app  on your Mac, try these suggestions.


If a specific mailbox is selected in the Favorites bar, Mail searches only that mailbox. To search all mailboxes instead, click All.
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].
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.
This solution can take quite some time because all messages will be deleted from your Mac. Therefore, it’s wise to try the other methods first if your mailbox is particularly large. To rebuild a mailbox, proceed as follows: 

In Mail, select the desired Mailbox from the left-hand panel.
From the Mailbox menu, choose Rebuild.