diff --git a/.env.example b/.env.example
index ff75466..9b5e733 100644
--- a/.env.example
+++ b/.env.example
@@ -17,3 +17,8 @@ POSTMARK_API_KEY=your_postmark_server_token
 BTCPAY_URL=https://payment.nxtgroup.org
 FROM_EMAIL=billing@nxtgroup.org
 BCC_EMAIL=admin@nxtgroup.org,finance@nxtgroup.org
+
+# Test Postmark after deploy (docker exec or Portainer console):
+#   python app.py test-email you@example.com
+# Or from host:
+#   curl -X POST "http://localhost:5000/test-email?token=YOUR_WEBHOOK_SECRET&to=you@example.com"
diff --git a/app.py b/app.py
index e1fd7c4..defd80f 100644
--- a/app.py
+++ b/app.py
@@ -58,6 +58,9 @@ def get_html_template(order_id, invoice_id, amount, currency, amount_paid, remai
     """
 
 def send_postmark_email(to_email, subject, html_body):
+    if not POSTMARK_API_KEY:
+        return {"ok": False, "status_code": None, "error": "POSTMARK_API_KEY is not set"}
+
     headers = {
         "Accept": "application/json",
         "Content-Type": "application/json",
@@ -71,9 +74,18 @@ def send_postmark_email(to_email, subject, html_body):
         "HtmlBody": html_body,
         "MessageStream": "outbound"
     }
-    
+
     response = requests.post("https://api.postmarkapp.com/email", json=payload, headers=headers)
-    return response.status_code == 200
+    result = {"ok": response.status_code == 200, "status_code": response.status_code}
+    if not result["ok"]:
+        result["error"] = response.text
+    return result
+
+
+def send_test_email(to_email):
+    html_body = get_html_template("TEST-001", "test-invoice-id", 100.0, "USD", 50.0, 50.0)
+    subject = "BTCPay Mailer test email"
+    return send_postmark_email(to_email, subject, html_body)
 
 @app.route('/btcpay-webhook', methods=['POST'])
 def btcpay_webhook():
@@ -120,14 +132,46 @@ def btcpay_webhook():
         html_body = get_html_template(order_id, invoice_id, amount, currency, amount_paid, remaining)
         subject = f"Action Required: Partial payment received for Order #{order_id}"
         
-        email_sent = send_postmark_email(buyer_email, subject, html_body)
-        
-        if email_sent:
+        result = send_postmark_email(buyer_email, subject, html_body)
+
+        if result["ok"]:
             return jsonify({"status": "success", "message": "Partial payment email sent"}), 200
-        else:
-            return jsonify({"error": "Failed to send email via Postmark"}), 500
+        return jsonify({"error": "Failed to send email via Postmark", "details": result}), 500
 
     return jsonify({"status": "ignored", "reason": "Payment meets total or invoice not in New state"}), 200
 
+
+@app.route('/test-email', methods=['POST'])
+def test_email():
+    token = request.args.get('token')
+    if token != WEBHOOK_SECRET:
+        return jsonify({"error": "Unauthorized"}), 401
+
+    to_email = request.args.get('to') or request.json.get('to') if request.is_json else None
+    if not to_email:
+        return jsonify({"error": "Missing 'to' email address"}), 400
+
+    result = send_test_email(to_email)
+    if result["ok"]:
+        return jsonify({
+            "status": "success",
+            "message": f"Test email sent to {to_email}",
+            "from": FROM_EMAIL,
+            "bcc": BCC_EMAIL,
+        }), 200
+    return jsonify({"error": "Failed to send test email via Postmark", "details": result}), 500
+
+
 if __name__ == '__main__':
+    import sys
+
+    if len(sys.argv) >= 3 and sys.argv[1] == 'test-email':
+        to = sys.argv[2]
+        outcome = send_test_email(to)
+        if outcome["ok"]:
+            print(f"OK: test email sent to {to} (from {FROM_EMAIL}, bcc {BCC_EMAIL})")
+            sys.exit(0)
+        print(f"FAIL: {outcome}", file=sys.stderr)
+        sys.exit(1)
+
     app.run(host='0.0.0.0', port=5000)
\ No newline at end of file