How to implement sequential processing for process task/process component?



I want the process task "Send Mail" to execute sequentially and not in parallel. For e.g 100 jobs came in job queue for sending mail at a time so right now One IM executes this job in parallel. But I want it to be done in sequence. I checked Process components and can see "Exclusive per object" check box but I cant edit it. Is there other way of implementing this? Please help. Thanks in advance.