Salesforce Fact #713 | Email approval response in other languages
Email Approval response works with languages other than English as well. For example, for Portuguese, it works with the words 'Aprovar' or 'Rejeitar'. Reference: https://developer.salesforce.com/docs/atlas.en-us.salesforce_email_approval_faq.meta/salesforce_email_approval_faq/faq_email_approvals_can_i_respond.htm