[exim] How to set exim to manage the number of CC or BCC add…

Hi,
first of all I want to say hello to everybody in this list, very new around
here. If I do something wrong, I ask you to please teach me and not to ban
me.

Here is my question, I have some customers that are using my servers to send
emails to a bunch of people, not spam but customers and / or friends, but
some times the list of CC or BCC are hughe, yesterday I saw in my QUEUE
someone sending an email to 194 email accounts.

So, would you be very kind to tell me how to modify EXIM in order to only
left a customer to send 10 or 20 emails maximum?

Your answers are greatly appreciated.

Warm regards,

Sergio