2 mail server 1 domain name

I have planned to setup our network with 2 different types of mail server. 1 is in Linux (qmail) and 2 is in Microsoft (Exchange). But I have planned to keep only one domain name as well as 1 MX record for both.

In this certain users will be in qmail and certain will be in exchange.

Mails should be routed based on the users mail id.

If anybody have idea about this kindly please help me with procedure to be done.