FortiSanbox - Device Priority

Can you set a device priority? For example place on top of the job queue submissions from FortiMail, all other devices back of the queue.

Reason for asking is that we have a small number of VMs and we have configured FortiClients to use sandbox, so user submitted files are filling up queue and fortimail submitted files are waiting in queue, mail deivery is affected. 

I know there is a file submission priority, but has "device" and there is no way to differentiate the type of device.

Anthony