limiting number of recipients in email

[Marlon Anthony Abao]

hello, 
        am sure that this has been discussed here a gadzillion times, an i hope
one more time would not be so bad :)

        how does one go about limiting the number of recipients in the 'CC:" /
"BCC:" fields?  i don't want any of my subscribers to spam to the outside
world.
at least this way, they would at least be discouraged to do so.

-marlon