diff --git a/public/invoice-view.js b/public/invoice-view.js
index 5ac9782..3ebd91c 100644
--- a/public/invoice-view.js
+++ b/public/invoice-view.js
@@ -239,6 +239,17 @@ function renderInvoiceRow(invoice) {
         paidBtn = `<button onclick="window.paymentModal.open([${invoice.id}])" class="text-emerald-600 hover:text-emerald-800" title="Record Payment in QBO">💰 Payment</button>`;
     }
 
+    // Send status button — only for QBO invoices
+    let sendBtn = '';
+    if (hasQbo && !paid) {
+        const isSent = invoice.email_status === 'sent';
+        if (isSent) {
+            sendBtn = `<button onclick="window.invoiceView.setEmailStatus(${invoice.id}, 'open')" class="text-gray-400 hover:text-gray-600 text-xs" title="Mark as not sent">✉️ Sent</button>`;
+        } else {
+            sendBtn = `<button onclick="window.invoiceView.setEmailStatus(${invoice.id}, 'sent')" class="text-indigo-600 hover:text-indigo-800 text-xs" title="Mark as sent to customer">📤 Mark Sent</button>`;
+        }
+    }
+
     const delBtn = `<button onclick="window.invoiceView.remove(${invoice.id})" class="text-red-600 hover:text-red-900">Del</button>`;
 
     const rowClass = paid ? (invoice.payment_status === 'Deposited' ? 'bg-blue-50/50' : 'bg-green-50/50') : partial ? 'bg-yellow-50/30' : overdue ? 'bg-red-50/50' : '';
@@ -252,7 +263,7 @@ function renderInvoiceRow(invoice) {
             <td class="px-4 py-3 whitespace-nowrap text-sm text-gray-500">${invoice.terms}</td>
             <td class="px-4 py-3 whitespace-nowrap text-sm text-gray-900 font-semibold">${amountDisplay}</td>
             <td class="px-4 py-3 whitespace-nowrap text-sm font-medium space-x-1">
-                ${editBtn} ${qboBtn} ${pdfBtn} ${htmlBtn} ${paidBtn} ${delBtn}
+                ${editBtn} ${qboBtn} ${pdfBtn} ${htmlBtn} ${sendBtn} ${paidBtn} ${delBtn}
             </td>
         </tr>`;
 }
@@ -440,6 +451,23 @@ export async function syncFromQBO() {
     finally { if (typeof hideSpinner === 'function') hideSpinner(); }
 }
 
+export async function setEmailStatus(id, status) {
+    const label = status === 'sent' ? 'Mark as sent' : 'Mark as not sent';
+    if (!confirm(`${label}?`)) return;
+    if (typeof showSpinner === 'function') showSpinner(`Updating status in QBO...`);
+    try {
+        const r = await fetch(`/api/invoices/${id}/email-status`, {
+            method: 'PATCH',
+            headers: { 'Content-Type': 'application/json' },
+            body: JSON.stringify({ status })
+        });
+        const d = await r.json();
+        if (r.ok) loadInvoices();
+        else alert(`❌ ${d.error}`);
+    } catch (e) { alert('Network error.'); }
+    finally { if (typeof hideSpinner === 'function') hideSpinner(); }
+}
+
 export async function resetQbo(id) {
     if (!confirm('Reset QBO link?\nInvoice must be deleted in QBO first!')) return;
     try {
@@ -471,6 +499,6 @@ export async function remove(id) {
 // ============================================================
 
 window.invoiceView = {
-    viewPDF, viewHTML, exportToQBO, syncToQBO, syncFromQBO, resetQbo, markPaid, edit, remove,
+    viewPDF, viewHTML, syncFromQBO, resetQbo, markPaid, setEmailStatus, edit, remove,
     loadInvoices, renderInvoiceView, setStatus
 };
\ No newline at end of file
diff --git a/server.js b/server.js
index 3dd3f70..56d59f0 100644
--- a/server.js
+++ b/server.js
@@ -177,7 +177,7 @@ async function exportInvoiceToQbo(invoiceId, client) {
         "TxnDate": invoice.invoice_date.toISOString().split('T')[0],
         "Line": lineItems,
         "CustomerMemo": { "value": invoice.auth_code ? `Auth: ${invoice.auth_code}` : "" },
-        "EmailStatus": "EmailSent",
+        "EmailStatus": "NotSet",
         "BillEmail": { "Address": invoice.email || "" }
     };
 
@@ -292,7 +292,6 @@ async function syncInvoiceToQbo(invoiceId, client) {
 }
 
 
-
 // Logo endpoints
 app.get('/api/logo-info', async (req, res) => {
     try {
@@ -833,6 +832,7 @@ app.post('/api/invoices', async (req, res) => {
     }
 });
 
+
 app.post('/api/quotes/:id/convert-to-invoice', async (req, res) => {
     const { id } = req.params;
     
@@ -1062,6 +1062,69 @@ app.delete('/api/invoices/:id', async (req, res) => {
     }
 });
 
+app.patch('/api/invoices/:id/email-status', async (req, res) => {
+    const { id } = req.params;
+    const { status } = req.body; // 'sent' or 'open'
+
+    if (!['sent', 'open'].includes(status)) {
+        return res.status(400).json({ error: 'Status must be "sent" or "open".' });
+    }
+
+    try {
+        const invResult = await pool.query('SELECT qbo_id FROM invoices WHERE id = $1', [id]);
+        if (invResult.rows.length === 0) return res.status(404).json({ error: 'Invoice not found' });
+
+        const invoice = invResult.rows[0];
+
+        // QBO updaten falls vorhanden
+        if (invoice.qbo_id) {
+            const oauthClient = getOAuthClient();
+            const companyId = oauthClient.getToken().realmId;
+            const baseUrl = process.env.QBO_ENVIRONMENT === 'production'
+                ? 'https://quickbooks.api.intuit.com'
+                : 'https://sandbox-quickbooks.api.intuit.com';
+
+            // SyncToken holen
+            const qboRes = await makeQboApiCall({
+                url: `${baseUrl}/v3/company/${companyId}/invoice/${invoice.qbo_id}`,
+                method: 'GET'
+            });
+            const qboData = qboRes.getJson ? qboRes.getJson() : qboRes.json;
+            const syncToken = qboData.Invoice?.SyncToken;
+
+            if (syncToken !== undefined) {
+                const emailStatus = status === 'sent' ? 'EmailSent' : 'NotSet';
+
+                await makeQboApiCall({
+                    url: `${baseUrl}/v3/company/${companyId}/invoice`,
+                    method: 'POST',
+                    headers: { 'Content-Type': 'application/json' },
+                    body: JSON.stringify({
+                        Id: invoice.qbo_id,
+                        SyncToken: syncToken,
+                        sparse: true,
+                        EmailStatus: emailStatus
+                    })
+                });
+
+                console.log(`✅ QBO Invoice ${invoice.qbo_id} email status → ${emailStatus}`);
+            }
+        }
+
+        // Lokal updaten
+        await pool.query(
+            'UPDATE invoices SET email_status = $1, updated_at = CURRENT_TIMESTAMP WHERE id = $2',
+            [status, id]
+        );
+
+        res.json({ success: true, status });
+
+    } catch (error) {
+        console.error('Error updating email status:', error);
+        res.status(500).json({ error: 'Failed to update status: ' + error.message });
+    }
+});
+
 // PDF Generation code continues below...
 
 // PDF Generation using templates and persistent browser