diff --git a/docker-compose.prod.yml b/docker-compose.prod.yml
index bc467382e..addfef2d2 100644
--- a/docker-compose.prod.yml
+++ b/docker-compose.prod.yml
@@ -33,6 +33,13 @@ services:
       - EMAIL_PROVIDER=${EMAIL_PROVIDER:-resend}
       - RESEND_API_KEY=${RESEND_API_KEY:-}
       - SMTP_FROM=${SMTP_FROM:-noreply@trinity.example.com}
+      # SMTP transport (EMAIL_PROVIDER=smtp) — read by src/backend/config.py (#771)
+      - SMTP_HOST=${SMTP_HOST:-}
+      - SMTP_PORT=${SMTP_PORT:-587}
+      - SMTP_USER=${SMTP_USER:-}
+      - SMTP_PASSWORD=${SMTP_PASSWORD:-}
+      # SendGrid transport (EMAIL_PROVIDER=sendgrid) — read by src/backend/config.py (#771)
+      - SENDGRID_API_KEY=${SENDGRID_API_KEY:-}
       - GITHUB_CLIENT_ID=${GITHUB_CLIENT_ID}
       - GITHUB_CLIENT_SECRET=${GITHUB_CLIENT_SECRET}
       - NOTION_CLIENT_ID=${NOTION_CLIENT_ID}
diff --git a/docker-compose.yml b/docker-compose.yml
index fbdb9b189..e4717772e 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -32,6 +32,13 @@ services:
       - EMAIL_PROVIDER=${EMAIL_PROVIDER:-resend}
       - RESEND_API_KEY=${RESEND_API_KEY:-}
       - SMTP_FROM=${SMTP_FROM:-noreply@trinity.example.com}
+      # SMTP transport (EMAIL_PROVIDER=smtp) — read by src/backend/config.py (#771)
+      - SMTP_HOST=${SMTP_HOST:-}
+      - SMTP_PORT=${SMTP_PORT:-587}
+      - SMTP_USER=${SMTP_USER:-}
+      - SMTP_PASSWORD=${SMTP_PASSWORD:-}
+      # SendGrid transport (EMAIL_PROVIDER=sendgrid) — read by src/backend/config.py (#771)
+      - SENDGRID_API_KEY=${SENDGRID_API_KEY:-}
       # Log Retention & Archival Configuration
       - LOG_RETENTION_DAYS=${LOG_RETENTION_DAYS:-90}
       - LOG_ARCHIVE_ENABLED=${LOG_ARCHIVE_ENABLED:-true}
diff --git a/tests/unit/test_slot_per_slot_ttl.py b/tests/unit/test_slot_per_slot_ttl.py
index ccaa8494f..f1fdf2900 100644
--- a/tests/unit/test_slot_per_slot_ttl.py
+++ b/tests/unit/test_slot_per_slot_ttl.py
@@ -47,10 +47,29 @@
     sys.path.insert(0, str(_BACKEND))
 
 
+# Modules this test stubs into sys.modules (directly or via the
+# importlib-loaded slot_service_direct / cleanup_service_direct helpers)
+# — restored after each test so they don't leak into other test files in
+# the same pytest session. Declaring this at module level (paired with
+# the `_restore_sys_modules` fixture below) is the sanctioned
+# snapshot/restore pattern recognised by tests/lint_sys_modules.py
+# (precedent: tests/unit/test_telegram_webhook_backfill.py).
+_STUBBED_MODULE_NAMES = [
+    "config",
+    "redis",
+    "utils.helpers",
+    "utils.credential_sanitizer",
+    "database",
+    "models",
+    "services.capacity_manager",
+    "slot_service_direct",
+    "cleanup_service_direct",
+]
+
+
 @pytest.fixture(autouse=True)
 def _restore_sys_modules():
-    names = ["config", "slot_service_direct", "utils.helpers", "redis"]
-    saved = {n: sys.modules.get(n) for n in names}
+    saved = {n: sys.modules.get(n) for n in _STUBBED_MODULE_NAMES}
     try:
         yield
     finally: