I am planning to install Zimbra server to handle email on a new server I have in my office. Currently, I use Drupal 6 which is hosted with my domain hosting company on a Linux VMWare Cloud VPS type package. The website uses various forms and has a booking system which has the ability to send out emails. I know I will have to redirect the MX records to the IP address of the Zimbra server.

Do I need to make any configuration changes in Drupal to force it to use Zimbra, or will it simply continue using its own internal SMTP engine?

Many thanks...