Hello,
If you use Directadmin to manage services on your Linux server including SMTP, POP3, IMAP... then I'm almost sure there are no server's side limits which would prevent emails from showing up via POP, IMAP protocols. At least by default all the existing emails should be available for reading via IMAP and POP3 protocols.
If Outlook does not show emails older than N-days, then you need to check Outlook preferences.