diff --git a/src/client/components/admin-bookings.tsx b/src/client/components/admin-bookings.tsx
index 610db15..b7e07ad 100644
--- a/src/client/components/admin-bookings.tsx
+++ b/src/client/components/admin-bookings.tsx
@@ -7,6 +7,8 @@ export function AdminBookings() {
   const [selectedPhoto, setSelectedPhoto] = useState<string>("");
   const [showPhotoModal, setShowPhotoModal] = useState(false);
   const [showCancelConfirm, setShowCancelConfirm] = useState<string | null>(null);
+  const [showMessageModal, setShowMessageModal] = useState<string | null>(null);
+  const [messageText, setMessageText] = useState<string>("");
   const [successMsg, setSuccessMsg] = useState<string>("");
   const [errorMsg, setErrorMsg] = useState<string>("");
 
@@ -49,6 +51,19 @@ export function AdminBookings() {
     })
   );
 
+  const { mutate: sendMessage, isPending: isSendingMessage } = useMutation(
+    queryClient.bookings.sendCustomerMessage.mutationOptions({
+      onSuccess: () => {
+        setSuccessMsg("Nachricht wurde erfolgreich gesendet.");
+        setShowMessageModal(null);
+        setMessageText("");
+      },
+      onError: (error: any) => {
+        setErrorMsg(error?.message || "Fehler beim Senden der Nachricht.");
+      }
+    })
+  );
+
   const getTreatmentName = (treatmentId: string) => {
      return treatments?.find(t => t.id === treatmentId)?.name || "Unbekannte Behandlung";
   };
@@ -83,6 +98,35 @@ export function AdminBookings() {
     setSelectedPhoto("");
   };
 
+  const openMessageModal = (bookingId: string) => {
+    setShowMessageModal(bookingId);
+    setMessageText("");
+  };
+
+  const closeMessageModal = () => {
+    setShowMessageModal(null);
+    setMessageText("");
+  };
+
+  const handleSendMessage = () => {
+    if (!showMessageModal || !messageText.trim()) {
+      setErrorMsg("Bitte gib eine Nachricht ein.");
+      return;
+    }
+    
+    sendMessage({
+      sessionId: localStorage.getItem("sessionId") || "",
+      bookingId: showMessageModal,
+      message: messageText.trim(),
+    });
+  };
+
+  // Check if booking is in the future
+  const isFutureBooking = (appointmentDate: string) => {
+    const today = new Date().toISOString().split("T")[0];
+    return appointmentDate >= today;
+  };
+
   const filteredBookings = bookings?.filter(booking => 
     selectedDate ? booking.appointmentDate === selectedDate : true
   ).sort((a, b) => {
@@ -251,45 +295,57 @@ export function AdminBookings() {
                   </span>
                 </td>
                 <td className="px-6 py-4 whitespace-nowrap text-sm font-medium">
-                  <div className="flex space-x-2">
-                    {booking.status === "pending" && (
-                      <>
+                  <div className="flex flex-col space-y-2">
+                    <div className="flex space-x-2">
+                      {booking.status === "pending" && (
+                        <>
+                          <button
+                            onClick={() => updateBookingStatus({ sessionId: localStorage.getItem("sessionId") || "", id: booking.id, status: "confirmed" })}
+                            className="text-green-600 hover:text-green-900"
+                          >
+                            Confirm
+                          </button>
+                          <button
+                            onClick={() => setShowCancelConfirm(booking.id)}
+                            className="text-red-600 hover:text-red-900"
+                          >
+                            Cancel
+                          </button>
+                        </>
+                      )}
+                      {booking.status === "confirmed" && (
+                        <>
+                          <button
+                            onClick={() => updateBookingStatus({ sessionId: localStorage.getItem("sessionId") || "", id: booking.id, status: "completed" })}
+                            className="text-blue-600 hover:text-blue-900"
+                          >
+                            Complete
+                          </button>
+                          <button
+                            onClick={() => setShowCancelConfirm(booking.id)}
+                            className="text-red-600 hover:text-red-900"
+                          >
+                            Cancel
+                          </button>
+                        </>
+                      )}
+                      {(booking.status === "cancelled" || booking.status === "completed") && (
                         <button
                           onClick={() => updateBookingStatus({ sessionId: localStorage.getItem("sessionId") || "", id: booking.id, status: "confirmed" })}
                           className="text-green-600 hover:text-green-900"
                         >
-                          Confirm
+                          Reactivate
                         </button>
-                        <button
-                          onClick={() => setShowCancelConfirm(booking.id)}
-                          className="text-red-600 hover:text-red-900"
-                        >
-                          Cancel
-                        </button>
-                      </>
-                    )}
-                    {booking.status === "confirmed" && (
-                      <>
-                        <button
-                          onClick={() => updateBookingStatus({ sessionId: localStorage.getItem("sessionId") || "", id: booking.id, status: "completed" })}
-                          className="text-blue-600 hover:text-blue-900"
-                        >
-                          Complete
-                        </button>
-                        <button
-                          onClick={() => setShowCancelConfirm(booking.id)}
-                          className="text-red-600 hover:text-red-900"
-                        >
-                          Cancel
-                        </button>
-                      </>
-                    )}
-                    {(booking.status === "cancelled" || booking.status === "completed") && (
+                      )}
+                    </div>
+                    {/* Show message button for future bookings with email */}
+                    {isFutureBooking(booking.appointmentDate) && booking.customerEmail && (
                       <button
-                        onClick={() => updateBookingStatus({ sessionId: localStorage.getItem("sessionId") || "", id: booking.id, status: "confirmed" })}
-                        className="text-green-600 hover:text-green-900"
+                        onClick={() => openMessageModal(booking.id)}
+                        className="text-pink-600 hover:text-pink-900 text-left"
+                        title="Nachricht an Kunden senden"
                       >
-                        Reactivate
+                        💬 Nachricht
                       </button>
                     )}
                   </div>
@@ -369,6 +425,87 @@ export function AdminBookings() {
           </div>
         </div>
       )}
+
+      {/* Message Modal */}
+      {showMessageModal && (
+        <div className="fixed inset-0 bg-black bg-opacity-50 flex items-center justify-center z-50">
+          <div className="bg-white rounded-lg p-6 max-w-2xl w-full mx-4">
+            <div className="flex justify-between items-center mb-4">
+              <h3 className="text-lg font-medium text-gray-900">Nachricht an Kunden senden</h3>
+              <button
+                onClick={closeMessageModal}
+                className="text-gray-400 hover:text-gray-600 text-2xl"
+                disabled={isSendingMessage}
+              >
+                ×
+              </button>
+            </div>
+            
+            {(() => {
+              const booking = bookings?.find(b => b.id === showMessageModal);
+              if (!booking) return null;
+              
+              return (
+                <div className="mb-4 bg-gray-50 p-4 rounded-md">
+                  <p className="text-sm text-gray-700">
+                    <strong>Kunde:</strong> {booking.customerName}
+                  </p>
+                  <p className="text-sm text-gray-700">
+                    <strong>E-Mail:</strong> {booking.customerEmail}
+                  </p>
+                  <p className="text-sm text-gray-700">
+                    <strong>Termin:</strong> {new Date(booking.appointmentDate).toLocaleDateString()} um {booking.appointmentTime}
+                  </p>
+                  <p className="text-sm text-gray-700">
+                    <strong>Behandlung:</strong> {getTreatmentName(booking.treatmentId)}
+                  </p>
+                </div>
+              );
+            })()}
+            
+            <div className="mb-4">
+              <label className="block text-sm font-medium text-gray-700 mb-2">
+                Deine Nachricht
+              </label>
+              <textarea
+                value={messageText}
+                onChange={(e) => setMessageText(e.target.value)}
+                placeholder="Schreibe hier deine Nachricht an den Kunden..."
+                rows={6}
+                maxLength={5000}
+                className="w-full p-3 border border-gray-300 rounded-md focus:ring-2 focus:ring-pink-500 focus:border-pink-500"
+                disabled={isSendingMessage}
+              />
+              <p className="text-xs text-gray-500 mt-1">
+                {messageText.length} / 5000 Zeichen
+              </p>
+            </div>
+            
+            <div className="bg-blue-50 border-l-4 border-blue-400 p-3 mb-4">
+              <p className="text-sm text-blue-700">
+                💡 <strong>Hinweis:</strong> Der Kunde kann direkt auf diese E-Mail antworten. Die Antwort geht an die in den Einstellungen hinterlegte Admin-E-Mail-Adresse.
+              </p>
+            </div>
+            
+            <div className="flex space-x-3">
+              <button
+                onClick={handleSendMessage}
+                disabled={isSendingMessage || !messageText.trim()}
+                className="flex-1 bg-pink-600 text-white py-2 px-4 rounded-md hover:bg-pink-700 transition-colors disabled:bg-gray-300 disabled:cursor-not-allowed"
+              >
+                {isSendingMessage ? "Wird gesendet..." : "Nachricht senden"}
+              </button>
+              <button
+                onClick={closeMessageModal}
+                disabled={isSendingMessage}
+                className="flex-1 bg-gray-200 text-gray-800 py-2 px-4 rounded-md hover:bg-gray-300 transition-colors disabled:bg-gray-100 disabled:cursor-not-allowed"
+              >
+                Abbrechen
+              </button>
+            </div>
+          </div>
+        </div>
+      )}
     </div>
   );
 }
\ No newline at end of file
diff --git a/src/server/lib/email-templates.ts b/src/server/lib/email-templates.ts
index a4727aa..b5c95c8 100644
--- a/src/server/lib/email-templates.ts
+++ b/src/server/lib/email-templates.ts
@@ -347,3 +347,43 @@ export async function renderAdminRescheduleExpiredHTML(params: {
   return renderBrandedEmail("Abgelaufene Terminänderungsvorschläge", inner);
 }
 
+export async function renderCustomerMessageHTML(params: {
+  customerName: string;
+  message: string;
+  appointmentDate?: string;
+  appointmentTime?: string;
+  treatmentName?: string;
+}) {
+  const { customerName, message, appointmentDate, appointmentTime, treatmentName } = params;
+  const formattedDate = appointmentDate ? formatDateGerman(appointmentDate) : null;
+  const domain = process.env.DOMAIN || 'localhost:5173';
+  const protocol = domain.includes('localhost') ? 'http' : 'https';
+  const legalUrl = `${protocol}://${domain}/legal`;
+  const ownerName = process.env.OWNER_NAME || 'Stargirlnails Kiel';
+  
+  const inner = `
+    <p>Hallo ${customerName},</p>
+    ${(appointmentDate && appointmentTime && treatmentName) ? `
+    <div style="background-color: #f8fafc; border-left: 4px solid #db2777; padding: 16px; margin: 20px 0; border-radius: 4px;">
+      <p style="margin: 0; font-weight: 600; color: #db2777;">📅 Zu deinem Termin:</p>
+      <ul style="margin: 8px 0 0 0; color: #475569; list-style: none; padding: 0;">
+        <li><strong>Behandlung:</strong> ${treatmentName}</li>
+        <li><strong>Datum:</strong> ${formattedDate}</li>
+        <li><strong>Uhrzeit:</strong> ${appointmentTime}</li>
+      </ul>
+    </div>
+    ` : ''}
+    <div style="background-color: #fef9f5; border-left: 4px solid #f59e0b; padding: 16px; margin: 20px 0; border-radius: 4px;">
+      <p style="margin: 0; font-weight: 600; color: #f59e0b;">💬 Nachricht von ${ownerName}:</p>
+      <div style="margin: 12px 0 0 0; color: #475569; white-space: pre-wrap; line-height: 1.6;">${message.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;')}</div>
+    </div>
+    <p>Bei Fragen oder Anliegen kannst du einfach auf diese E-Mail antworten – wir helfen dir gerne weiter!</p>
+    <div style="background-color: #f8fafc; border-left: 4px solid #3b82f6; padding: 16px; margin: 20px 0; border-radius: 4px;">
+      <p style="margin: 0; font-weight: 600; color: #3b82f6;">📋 Rechtliche Informationen:</p>
+      <p style="margin: 8px 0 12px 0; color: #475569;">Weitere Informationen findest du in unserem <a href="${legalUrl}" style="color: #3b82f6; text-decoration: underline;">Impressum und Datenschutz</a>.</p>
+    </div>
+    <p>Liebe Grüße,<br/>${ownerName}</p>
+  `;
+  return renderBrandedEmail("Nachricht zu deinem Termin", inner);
+}
+
diff --git a/src/server/lib/email.ts b/src/server/lib/email.ts
index bedd7a7..d378c4b 100644
--- a/src/server/lib/email.ts
+++ b/src/server/lib/email.ts
@@ -6,6 +6,7 @@ type SendEmailParams = {
   from?: string;
   cc?: string | string[];
   bcc?: string | string[];
+  replyTo?: string | string[];
   attachments?: Array<{
     filename: string;
     content: string; // base64 encoded
@@ -130,22 +131,27 @@ export async function sendEmail(params: SendEmailParams): Promise<{ success: boo
     return { success: false };
   }
 
+  const payload = {
+    from: params.from || DEFAULT_FROM,
+    to: Array.isArray(params.to) ? params.to : [params.to],
+    subject: params.subject,
+    text: params.text,
+    html: params.html,
+    cc: params.cc ? (Array.isArray(params.cc) ? params.cc : [params.cc]) : undefined,
+    bcc: params.bcc ? (Array.isArray(params.bcc) ? params.bcc : [params.bcc]) : undefined,
+    reply_to: params.replyTo ? (Array.isArray(params.replyTo) ? params.replyTo : [params.replyTo]) : undefined,
+    attachments: params.attachments,
+  };
+
+  console.log(`Sending email via Resend: to=${JSON.stringify(payload.to)}, subject="${params.subject}"`);
+
   const response = await fetch("https://api.resend.com/emails", {
     method: "POST",
     headers: {
       "Authorization": `Bearer ${RESEND_API_KEY}`,
       "Content-Type": "application/json",
     },
-    body: JSON.stringify({
-      from: params.from || DEFAULT_FROM,
-      to: Array.isArray(params.to) ? params.to : [params.to],
-      subject: params.subject,
-      text: params.text,
-      html: params.html,
-      cc: params.cc ? (Array.isArray(params.cc) ? params.cc : [params.cc]) : undefined,
-      bcc: params.bcc ? (Array.isArray(params.bcc) ? params.bcc : [params.bcc]) : undefined,
-      attachments: params.attachments,
-    }),
+    body: JSON.stringify(payload),
   });
 
   if (!response.ok) {
@@ -153,6 +159,9 @@ export async function sendEmail(params: SendEmailParams): Promise<{ success: boo
     console.error("Resend send error:", response.status, body);
     return { success: false };
   }
+  
+  const responseData = await response.json().catch(() => ({}));
+  console.log("Resend email sent successfully:", responseData);
   return { success: true };
 }
 
diff --git a/src/server/rpc/bookings.ts b/src/server/rpc/bookings.ts
index efe2d61..af6c19c 100644
--- a/src/server/rpc/bookings.ts
+++ b/src/server/rpc/bookings.ts
@@ -3,7 +3,7 @@ import { z } from "zod";
 import { randomUUID } from "crypto";
 import { createKV } from "../lib/create-kv.js";
 import { sendEmail, sendEmailWithAGB, sendEmailWithAGBAndCalendar, sendEmailWithInspirationPhoto } from "../lib/email.js";
-import { renderBookingPendingHTML, renderBookingConfirmedHTML, renderBookingCancelledHTML, renderAdminBookingNotificationHTML, renderBookingRescheduleProposalHTML, renderAdminRescheduleAcceptedHTML, renderAdminRescheduleDeclinedHTML } from "../lib/email-templates.js";
+import { renderBookingPendingHTML, renderBookingConfirmedHTML, renderBookingCancelledHTML, renderAdminBookingNotificationHTML, renderBookingRescheduleProposalHTML, renderAdminRescheduleAcceptedHTML, renderAdminRescheduleDeclinedHTML, renderCustomerMessageHTML } from "../lib/email-templates.js";
 import { router as rootRouter } from "./index.js";
 import { createORPCClient } from "@orpc/client";
 import { RPCLink } from "@orpc/client/fetch";
@@ -911,4 +911,74 @@ export const router = {
         }
       };
     }),
+
+  // Admin sendet Nachricht an Kunden
+  sendCustomerMessage: os
+    .input(z.object({
+      sessionId: z.string(),
+      bookingId: z.string(),
+      message: z.string().min(1, "Nachricht darf nicht leer sein").max(5000, "Nachricht ist zu lang (max. 5000 Zeichen)"),
+    }))
+    .handler(async ({ input }) => {
+      await assertOwner(input.sessionId);
+      
+      const booking = await kv.getItem(input.bookingId);
+      if (!booking) throw new Error("Buchung nicht gefunden");
+      
+      // Check if booking has customer email
+      if (!booking.customerEmail) {
+        throw new Error("Diese Buchung hat keine E-Mail-Adresse. Bitte kontaktiere den Kunden telefonisch.");
+      }
+      
+      // Check if booking is in the future
+      const today = new Date().toISOString().split("T")[0];
+      const bookingDate = booking.appointmentDate;
+      if (bookingDate < today) {
+        throw new Error("Nachrichten können nur für zukünftige Termine gesendet werden.");
+      }
+      
+      // Get treatment name for context
+      const treatment = await treatmentsKV.getItem(booking.treatmentId);
+      const treatmentName = treatment?.name || "Behandlung";
+      
+      // Prepare email with Reply-To header
+      const ownerName = process.env.OWNER_NAME || "Stargirlnails Kiel";
+      const emailFrom = process.env.EMAIL_FROM || "Stargirlnails <no-reply@stargirlnails.de>";
+      const replyToEmail = process.env.ADMIN_EMAIL;
+      
+      const formattedDate = formatDateGerman(bookingDate);
+      
+      const html = await renderCustomerMessageHTML({
+        customerName: booking.customerName,
+        message: input.message,
+        appointmentDate: bookingDate,
+        appointmentTime: booking.appointmentTime,
+        treatmentName: treatmentName,
+      });
+      
+      const textContent = `Hallo ${booking.customerName},\n\nZu deinem Termin:\nBehandlung: ${treatmentName}\nDatum: ${formattedDate}\nUhrzeit: ${booking.appointmentTime}\n\nNachricht von ${ownerName}:\n${input.message}\n\nBei Fragen oder Anliegen kannst du einfach auf diese E-Mail antworten – wir helfen dir gerne weiter!\n\nLiebe Grüße,\n${ownerName}`;
+      
+      // Send email with BCC to admin for monitoring
+      // Note: Not using explicit 'from' or 'replyTo' to match behavior of other system emails
+      console.log(`Sending customer message to ${booking.customerEmail} for booking ${input.bookingId}`);
+      console.log(`Email config: from=${emailFrom}, replyTo=${replyToEmail}, bcc=${replyToEmail}`);
+      const emailResult = await sendEmail({
+        to: booking.customerEmail,
+        subject: `Nachricht zu deinem Termin am ${formattedDate}`,
+        text: textContent,
+        html: html,
+        bcc: replyToEmail ? [replyToEmail] : undefined,
+      });
+      
+      if (!emailResult.success) {
+        console.error(`Failed to send customer message to ${booking.customerEmail}`);
+        throw new Error("E-Mail konnte nicht versendet werden. Bitte überprüfe die E-Mail-Konfiguration oder versuche es später erneut.");
+      }
+      
+      console.log(`Successfully sent customer message to ${booking.customerEmail}`);
+      return { 
+        success: true, 
+        message: `Nachricht wurde erfolgreich an ${booking.customerEmail} gesendet.`
+      };
+    }),
 };
\ No newline at end of file