Same domain exist on fortimail and microsoft exchange

1 - we have fortimail 2000a & microsoft exchange related to the same domain 

2 - some mailboxes exist on fortimail and others on exchange  

3 - for example how to deliver mails from x@abc.com on fortimail to y@abc.com on exchange 

Note : 1 - fortimail configured as server mode .

          2 - already we configure it on exchange and it is working well .