diff --git a/modules/mailu/module.json b/modules/mailu/module.json
index b4cc6b2c..24ef2fe5 100644
--- a/modules/mailu/module.json
+++ b/modules/mailu/module.json
@@ -5,6 +5,10 @@
     "policy": "record",
     "why": "people's mail: any change to how its containers are declared recreates them together in one send, and the mail is down for everyone until they are up again — a person chooses the moment (hq ADR 0242, issue 295)"
   },
+  "unhealthy": {
+    "severity": "urgent",
+    "why": "while mailu is broken, mail is refused or stuck for everyone with a mailbox here (hq ADR 0355, issue 687)"
+  },
   "capabilities": [
     "container-runtime"
   ],