Could you elaborate on the feasibility of sending Automated Clearing House (ACH) transactions internationally? I understand that ACH is a domestic network primarily used in the United States for electronic funds transfer between financial institutions. However, given the globalization of the financial system, does ACH offer any cross-border capabilities? If not, what are the alternatives for international payments that are both cost-effective and reliable? Also, could you provide any insights into the potential challenges or limitations of sending ACH transactions internationally, if such a service exists?