Not all emails from outlook365 migrated to my new zoho account

Not all emails from outlook365 migrated to my new zoho account

I recently setup a new email address hosted by zoho.  I migrated all my folders and email from my Outlook365 account to my new zoho account, but not all my emails migrated.  Looks like only the past 12 months, or so, made the move.  How do I get the rest of my emails to migrate from 365 to zoho?