This is expected behaviour. In Outlook, the Company field is just plain text, but in Dynamics 365, the Company Name field on a Contact is a lookup to an Account. Because of that, it will only sync if Dynamics can find an Account with the exact same name, or if the system is configured to automatically create the Account. Check your Contact Synchronization Field Mappings and make sure “Company” maps to ParentCustomerId, and enable “Create parent account for new contacts” if you want Dynamics to auto-create the Account when one doesn’t already exist.