The subject wants to ask, "Is the overdue collection letter of China Merchants Bank's credit card sent by SF Express?" The overdue dunning letter issued by China Merchants Bank Credit Card was not issued by SF. The overdue dunning letter of China Merchants Bank's credit card does not need SF Express, but EMS can be used. The use of courier companies to send reminders requires payment of postage and courier fees, which increases the cost. In contrast, EMS can control costs and reduce operating costs.