I have a policy that uses monitor sets to email me when free space on the c: drive is below 10%. I would like to create a exception group for computers that I don't want to be alerted to this condition. I am not sure how to do this and am looking for ideas.
My first guess would to be modify the view that you have assigned to it. If you create a copy of the original and then within the advanced filters do a NOT THISGROUP or NOT COMP1 AND NOT COMP2 AND NOT COMP3.
Sorry, I'm rushing this response. Hope it makes sense!
I agree with Rshaw - you can certainly get deeper into this with the use of machine groups for assignment or go further in detail to run a procedure, rather than sending an email, that checks for Custom Field exclusions.
You might want to give my blog a read - it deals with the need to control when and where policies get applied, which, in turn, deploy the monitors.
We have a custom field which is basically "NoTenPercent" and the general policy to apply the 10% monitoring looks for "workstations where the NoTenPercent field isn't YES" (I'm simplifying this a bit). If we get a machine where we want to bypass that, there's an agent procedure whose job is just to apply that flag to the field. (And another to "undo" that in case we want to go back to 10% monitoring later.)