Hi Joe,
If you have a look at the system requirements for IBM Domino 9.0 you will see that you need Red Hat Enterprise Linux (RHEL) Server 6 x86-64 Update 3 or 4
XenServer is also not supported as a virtual platform but this shouldn't be any problem as I am running Domino 9.0 on XenServer 6.1 to.
Kind regards,
Dave