diff --git a/backend/app/services/email_service.py b/backend/app/services/email_service.py
new file mode 100644
index 00000000..94565970
--- /dev/null
+++ b/backend/app/services/email_service.py
@@ -0,0 +1,56 @@
+"""Email service: ACS amb dev fallback (log URL a consola)."""
+import logging
+from flask import current_app
+
+logger = logging.getLogger('mirofish.email')
+
+
+def send_invitation_email(to_email: str, to_name: str, accept_url: str) -> bool:
+    subject = "Invitació a MiroFish"
+    body = (
+        f"Hola {to_name},\n\n"
+        f"Has estat convidat/da a MiroFish.\n\n"
+        f"Estableix la teva contrasenya accedint a:\n{accept_url}\n\n"
+        f"Aquest enllaç caduca en {current_app.config['ACS_INVITATION_TTL_HOURS']} hores.\n"
+    )
+    return _send(to_email, subject, body)
+
+
+def send_reset_password_email(to_email: str, reset_url: str) -> bool:
+    subject = "Restabliment de contrasenya MiroFish"
+    body = (
+        f"Has sol·licitat restablir la contrasenya de MiroFish.\n\n"
+        f"Accedeix a:\n{reset_url}\n\n"
+        f"Aquest enllaç caduca en {current_app.config['ACS_RESET_PASSWORD_TTL_HOURS']} hora/es.\n"
+        f"Si no has fet aquesta sol·licitud, ignora aquest missatge.\n"
+    )
+    return _send(to_email, subject, body)
+
+
+def _send(to_email: str, subject: str, body: str) -> bool:
+    conn_str = current_app.config.get('ACS_CONNECTION_STRING', '')
+    sender = current_app.config.get('ACS_SENDER_ADDRESS', '')
+
+    if not conn_str:
+        logger.warning(
+            "[EMAIL DEV — ACS no configurat]\n"
+            f"  To:      {to_email}\n"
+            f"  Subject: {subject}\n"
+            f"  Body:\n{body}"
+        )
+        return True
+
+    try:
+        from azure.communication.email import EmailClient
+        client = EmailClient.from_connection_string(conn_str)
+        message = {
+            "senderAddress": sender,
+            "recipients": {"to": [{"address": to_email}]},
+            "content": {"subject": subject, "plainText": body},
+        }
+        poller = client.begin_send(message)
+        poller.result()
+        return True
+    except Exception as exc:
+        logger.error(f"ACS send failed to {to_email}: {exc}")
+        return False