Auto Email after after_workflow_action

Dear all ,

please find the below code i am trying send auto email after reject button but email is not going

frappe.ui.form.on(‘Purchase Order’, {
after_workflow_action: function (frm) {
if (frm.doc.workflow_state === ‘Draft’) {
frappe.prompt({
fieldname: ‘remarks’,
label: __(‘Enter Rejection Remarks’),
fieldtype: ‘Small Text’,
reqd: 1,
}, function (values) {
if (values.remarks) {
frm.doc.rejection_remarks = values.remarks;
frm.refresh_field(‘rejection_remarks’);

                var comment = frappe.model.get_new_doc('Comment');
                comment.comment_type = 'Comment';
                comment.reference_doctype = frm.doc.doctype;
                comment.reference_name = frm.doc.name;
                comment.comment_by = frappe.session.user;
                comment.content = values.remarks;

                frappe.call({
                    method: 'frappe.client.insert',
                    args: { doc: comment },
                    callback: function (r) {
                        if (!r.exc) {
                            frappe.msgprint(__('Comment added successfully.'));

                            // Send the email
                            frappe.sendmail({
                                recipients: 'kamal@example.com',
                                subject: 'Purchase Order Rejected: ' + frm.doc.name,
                                message: 'Your Purchase order has been Rejected.',
                                reference_doctype: frm.doc.doctype,
                                reference_name: frm.doc.name,
                                callback: function(response) {
                                    if (response.message === 'Email Sent') {
                                        frappe.msgprint('Email sent successfully.');
                                    } else {
                                        frappe.msgprint('Failed to send email: ' + response.message);
                                    }
                                },
                            });
                        } else {
                            frappe.msgprint(__('Error adding comment: ') + r.exc);
                        }
                    }
                });
            }
        });
    }
}

});

@KAMAL_DAS

Try with Notification > Value Change Method on Field Workflow State