diff --git a/examples/ticket_service/ticket_service.py b/examples/ticket_service/ticket_service.py
index 5810b3a..fae7001 100644
--- a/examples/ticket_service/ticket_service.py
+++ b/examples/ticket_service/ticket_service.py
@@ -34,12 +34,16 @@ from mas_core.generator import resource_local_part
 
 RESOURCE_TYPE = "ticket"
 INTAKE_TARGET = "ticket"
-_ALPHABET = "0123456789ABCDEFGHJKMNPQRSTVWXYZ"  # Crockford base32, no I L O U
+_ALPHABET = "0123456789abcdefghjkmnpqrstvwxyz"  # Crockford base32, no i l o u
 
 
 def default_ticket_id() -> str:
-    """Non-guessable-preferred, per the great-service statute."""
-    return "GS-" + "".join(secrets.choice(_ALPHABET) for _ in range(10))
+    """Non-guessable-preferred, per the great-service statute.
+
+    Lower case, so the address a customer sees is the one forwarders and
+    mailing lists deliver (spec 6.2, SCP-7).
+    """
+    return "gs-" + "".join(secrets.choice(_ALPHABET) for _ in range(10))
 
 
 SCHEMA = """
diff --git a/tests/test_end_to_end.py b/tests/test_end_to_end.py
index 194470a..8da7255 100644
--- a/tests/test_end_to_end.py
+++ b/tests/test_end_to_end.py
@@ -83,6 +83,12 @@ def test_canonical_lifecycle(env):
     assert len(svc.outbox()) == before and len(svc.quarantine()) == 1
 
 
+def test_default_ids_are_lower_case():
+    from ticket_service import default_ticket_id
+    tid = default_ticket_id()
+    assert tid == tid.lower() and tid.startswith("gs-") and len(tid) == 13
+
+
 def test_lower_cased_id_correlates(env):
     # IONOS forwards and Google Groups members arrive lower-cased (MAS-WP-0003 T04)
     svc, send, *_ = env