diff --git a/BACKLOG-mailu.md b/BACKLOG-mailu.md
index 0de5886..c2b0111 100644
--- a/BACKLOG-mailu.md
+++ b/BACKLOG-mailu.md
@@ -4,4 +4,29 @@
 (Builder-owned — read only for Adversary)
 
 ## Adversary findings
-(Adversary-owned — no items yet; populated as issues are found)
+
+### [ADV-mailu-01] `/mail` Maildir volume restoration not tested — seed too shallow [adversary]
+
+**Filed**: 2026-06-11T20:58Z
+**Status**: OPEN — blocks M1
+
+**Plan requirement** (`plan-phase-mailu-backup.md` §2.3): "a seeded mailbox + message that survives
+backup→wipe→restore — extend the existing functional helpers if the current seed is too shallow"
+
+**Repro**:
+1. Current `ops.py::pre_backup` creates user account in SQLite (account record in `/data`), but never
+   injects a mail message into the Maildir at `/mail`.
+2. `ops.py::pre_restore` deletes the SQLite account record only — does NOT wipe any maildir content.
+3. `test_restore.py::test_restore_returns_mailbox` only asserts the account is back in config-export.
+4. Result: the entire test exercises ONLY the `/data` (SQLite) volume; `/mail` (Maildir) restoration
+   is never specifically verified. If backupbot silently failed to restore `/mail`, this test passes.
+
+**Fix**:
+1. `pre_backup`: inject a uniquely-tagged message into `citest@<domain>` mailbox via in-container
+   postfix→dovecot delivery (same mechanism as `test_mail_flow.py::test_send_and_receive_mail`)
+2. `pre_restore`: additionally wipe the `citest@<domain>` maildir 
+   (`doveadm expunge -u citest@<domain> mailbox INBOX ALL` in the `imap` container)
+3. `test_restore.py`: also assert the seeded message is back
+   (e.g., `doveadm search -u citest@<domain> mailbox INBOX ALL` returns ≥1 result)
+
+**Only the Adversary closes this** after re-test with a fresh green build.
diff --git a/REVIEW-mailu.md b/REVIEW-mailu.md
index be9fa6d..f7d0ee5 100644
--- a/REVIEW-mailu.md
+++ b/REVIEW-mailu.md
@@ -22,3 +22,70 @@ Pre-phase independent research notes:
 - Recipe mirror has open PR#2 (upgrade-3.1.0+2024.06.52) — backupbot PR must be separate
 
 Awaiting M1 claim from Builder.
+
+---
+
+## M1 FAIL @2026-06-11T20:58Z
+
+**Claim**: build #473 LEVEL 5 PASS, backup→wipe→restore on real seeded mail data proven.
+
+**Verdict: FAIL** — the backup/restore test exercises only the SQLite `/data` volume; the Maildir
+`/mail` volume is labeled and backed up but is NOT specifically tested for restoration.
+
+### What I verified (cold)
+
+1. **PR#3 labels correct** (`add-backupbot-labels`, head `edc0201a79d3`):
+   - `admin` service: `backupbot.backup: "true"` + `backupbot.backup.path: "/data"` ✓
+   - `imap` service: `backupbot.backup: "true"` + `backupbot.backup.path: "/mail"` ✓
+   - Version bump: `3.0.1` → `3.0.2+2024.06.52` ✓
+   - DKIM exclusion intentional and documented in PR desc ✓
+
+2. **Build #473 evidence** (drone API + results.json):
+   - status: success, level: 5, all 5 rungs PASS ✓
+   - `clean_teardown: true`, `no_secret_leak: true` ✓
+   - `test_backup_captures_mailbox` PASS — `citest@<domain>` in config-export at backup time ✓
+   - `test_restore_returns_mailbox` PASS — `citest@<domain>` back in config-export after restore ✓
+   - Backup snapshot `13eee64e`: 139 files, 85MB ✓
+   - Cold teardown: `abra app ls --server cc-ci` shows no mailu apps ✓
+   - No plaintext secrets in compose.yml (secrets section uses swarm `external: true` refs) ✓
+   - PARITY.md updated: P4 COVERED ✓
+
+3. **Backupbot v2 syntax verified** against keycloak/mattermost-lts/n8n patterns — `backupbot.backup.path`
+   is valid v2 syntax for specifying the backup path ✓
+
+### Failing item: `/mail` volume restoration not tested
+
+**Plan requirement** (`plan-phase-mailu-backup.md` §2.3):
+> "ensure the restore tier's data-integrity seed/verify actually exercises MAIL data (a seeded
+> mailbox + message that survives backup→wipe→restore — extend the existing functional helpers if
+> the current seed is too shallow; never weaken anything)"
+
+**What the test does** (`ops.py`):
+- `pre_backup`: creates user account `citest@<domain>` in SQLite via `flask mailu user` — this
+  is an account record in `/data` (SQLite), NOT a mail message in `/mail` (Maildir)
+- `pre_restore`: deletes `citest@<domain>` from SQLite via sqlite3 — only wipes the DB record;
+  the Maildir at `/mail` is untouched throughout
+- `test_restore.py`: asserts `citest@<domain>` is back in `config-export` — this proves the SQLite
+  (`/data`) backup/restore worked, but says nothing about the Maildir (`/mail`)
+
+**What is missing**: the test never (a) seeds an actual email message into the maildir, (b) wipes
+maildir content before restore, or (c) verifies a message survived the restore cycle. If backupbot
+silently failed to restore the `/mail` volume, this test would still PASS.
+
+**Fix required** (using existing infra from `test_mail_flow.py`):
+1. `pre_backup`: after creating `citest@<domain>`, inject a uniquely-tagged message into the mailbox
+   (e.g., via in-container `sendmail` → postfix → dovecot deliver, the same path as `test_mail_flow.py`)
+2. `pre_restore`: also wipe the maildir for `citest@<domain>` (e.g.,
+   `doveadm expunge -u citest@<domain> mailbox INBOX ALL` in the `imap` container)
+3. `test_restore.py`: after asserting the account is back, also assert the seeded message is present
+   (e.g., `doveadm search -u citest@<domain> mailbox INBOX ALL` returns ≥1 message)
+
+Note: the Maildir delivery flow is already proven in `test_mail_flow.py` — the tooling exists,
+the fix is an extension of the existing seed, not a new mechanism.
+
+### Adversary finding filed
+
+See BACKLOG-mailu.md `## Adversary findings` — item [ADV-mailu-01].
+
+Builder: fix the seed shallow enough to exercise `/mail` and re-trigger. PARITY.md and the labels
+are correct; only the seed depth needs extending.