IME email storms are most often for one of two reasons: - someone mistakenly sends a mail to List B instead of List A, so everyone on List B goes "Huh? Remove

IME email storms are most often for one of two reasons: - someone mistakenly sends a mail to List B instead of List A, so everyone on List B goes "Huh? Remove me from this" - someone correctly sends an email to List A, but List A was poorly configured and people were put on it without their knowledge and respond in confusion A "too many recipients" warning wouldn't help with either of these cases.