diff --git a/.env.example b/.env.example
index 75a6e04..ff6ce24 100644
--- a/.env.example
+++ b/.env.example
@@ -57,8 +57,9 @@ PCM_API_SECRET=
 # Paste all of them comma-separated (also accepts single PCM_WEBHOOK_SECRET=).
 PCM_WEBHOOK_SECRETS=
 # PCM_WEBHOOK_SECRET=
-# Return address on every postcard order (JSON). Example:
-# PCM_RETURN_ADDRESS={"firstName":"Monica","lastName":"Dhillon","address":"123 Main St","city":"Naperville","state":"IL","zipCode":"60540"}
+# Required return address on every postcard order.
+# Quote the JSON (compose/shell break on bare {…, …}).
+# PCM_RETURN_ADDRESS='{"firstName":"Monica","lastName":"Dhillon","address":"123 Main St","city":"Naperville","state":"IL","zipCode":"60540"}'
 PCM_RETURN_ADDRESS=
 # Or set fields individually if JSON is empty:
 # PCM_RETURN_LINE1=
diff --git a/.env.prod.example b/.env.prod.example
index ff09205..6899694 100644
--- a/.env.prod.example
+++ b/.env.prod.example
@@ -66,8 +66,8 @@ PCM_API_SECRET=replace-me
 PCM_WEBHOOK_SECRETS=replace-me,replace-me-2
 # PCM_WEBHOOK_SECRET=replace-me  # optional single-secret alias
 
-# JSON return address for postcard orders
-PCM_RETURN_ADDRESS={"firstName":"Monica","lastName":"Dhillon","address":"replace-me","city":"replace-me","state":"IL","zipCode":"replace-me"}
+# JSON return address for postcard orders (quote so compose keeps commas)
+PCM_RETURN_ADDRESS='{"firstName":"Monica","lastName":"Dhillon","address":"replace-me","city":"replace-me","state":"IL","zipCode":"replace-me"}'
 # LOB_API_KEY=  # only if POSTCARD_PROVIDER=lob
 # CLICK2MAIL_API_KEY=
 # POSTGRID_API_KEY=
diff --git a/docker-compose.yml b/docker-compose.yml
index 44b710b..23a35bd 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -45,6 +45,19 @@ services:
       EMAIL_BACKEND: ${EMAIL_BACKEND:-django.core.mail.backends.console.EmailBackend}
       SMTP2GO_SMS_API_KEY: ${SMTP2GO_SMS_API_KEY:-}
       SMTP2GO_WEBHOOK_SECRET: ${SMTP2GO_WEBHOOK_SECRET:-}
+      POSTCARD_PROVIDER: ${POSTCARD_PROVIDER:-pcm}
+      PCM_API_KEY: ${PCM_API_KEY:-}
+      PCM_API_SECRET: ${PCM_API_SECRET:-}
+      PCM_CHILD_REF_NBR: ${PCM_CHILD_REF_NBR:-}
+      PCM_WEBHOOK_SECRETS: ${PCM_WEBHOOK_SECRETS:-}
+      PCM_WEBHOOK_SECRET: ${PCM_WEBHOOK_SECRET:-}
+      # Quote JSON in `.env`: PCM_RETURN_ADDRESS='{"firstName":"…",...}'
+      PCM_RETURN_ADDRESS: ${PCM_RETURN_ADDRESS:-}
+      PCM_RETURN_LINE1: ${PCM_RETURN_LINE1:-}
+      PCM_RETURN_LINE2: ${PCM_RETURN_LINE2:-}
+      PCM_RETURN_CITY: ${PCM_RETURN_CITY:-}
+      PCM_RETURN_STATE: ${PCM_RETURN_STATE:-}
+      PCM_RETURN_ZIP: ${PCM_RETURN_ZIP:-}
     depends_on:
       db:
         condition: service_healthy
@@ -70,6 +83,18 @@ services:
       EMAIL_BACKEND: ${EMAIL_BACKEND:-django.core.mail.backends.console.EmailBackend}
       SMTP2GO_SMS_API_KEY: ${SMTP2GO_SMS_API_KEY:-}
       SMTP2GO_WEBHOOK_SECRET: ${SMTP2GO_WEBHOOK_SECRET:-}
+      POSTCARD_PROVIDER: ${POSTCARD_PROVIDER:-pcm}
+      PCM_API_KEY: ${PCM_API_KEY:-}
+      PCM_API_SECRET: ${PCM_API_SECRET:-}
+      PCM_CHILD_REF_NBR: ${PCM_CHILD_REF_NBR:-}
+      PCM_WEBHOOK_SECRETS: ${PCM_WEBHOOK_SECRETS:-}
+      PCM_WEBHOOK_SECRET: ${PCM_WEBHOOK_SECRET:-}
+      PCM_RETURN_ADDRESS: ${PCM_RETURN_ADDRESS:-}
+      PCM_RETURN_LINE1: ${PCM_RETURN_LINE1:-}
+      PCM_RETURN_LINE2: ${PCM_RETURN_LINE2:-}
+      PCM_RETURN_CITY: ${PCM_RETURN_CITY:-}
+      PCM_RETURN_STATE: ${PCM_RETURN_STATE:-}
+      PCM_RETURN_ZIP: ${PCM_RETURN_ZIP:-}
     depends_on:
       db:
         condition: service_healthy
diff --git a/site/messaging/providers/postcard/pcm.py b/site/messaging/providers/postcard/pcm.py
index cb5c76c..097258b 100644
--- a/site/messaging/providers/postcard/pcm.py
+++ b/site/messaging/providers/postcard/pcm.py
@@ -193,38 +193,82 @@ def pcm_request(
 
 
 def return_address_from_settings() -> dict[str, str]:
-    """Build PCM returnAddress from PCM_RETURN_ADDRESS JSON or CONTACT_* vars."""
+    """Build PCM returnAddress from PCM_RETURN_ADDRESS JSON and/or PCM_RETURN_* vars.
+
+    PCM requires address/city/state (and zip) whenever firstName is set — an empty
+    street with SITE_NAME-derived firstName causes a 400 from POST /order/postcard.
+    """
+    data: dict[str, Any] = {}
     raw = (settings.PCM_RETURN_ADDRESS or "").strip()
     if raw:
-        data = json.loads(raw)
-        if not isinstance(data, dict):
+        try:
+            parsed = json.loads(raw)
+        except json.JSONDecodeError as exc:
+            raise PcmApiError(
+                "PCM_RETURN_ADDRESS must be valid JSON "
+                '(e.g. {"firstName":"…","lastName":"…","address":"…",'
+                '"city":"…","state":"IL","zipCode":"…"})'
+            ) from exc
+        if not isinstance(parsed, dict):
             raise PcmApiError("PCM_RETURN_ADDRESS must be a JSON object")
-        return {
-            "company": str(data.get("company") or ""),
-            "firstName": str(data.get("firstName") or data.get("first_name") or ""),
-            "lastName": str(data.get("lastName") or data.get("last_name") or ""),
-            "address": str(data.get("address") or data.get("line1") or ""),
-            "address2": str(data.get("address2") or data.get("line2") or ""),
-            "city": str(data.get("city") or ""),
-            "state": str(data.get("state") or ""),
-            "zipCode": str(data.get("zipCode") or data.get("zip") or ""),
-        }
+        data = parsed
 
     name = (settings.SITE_NAME or "").strip()
     parts = name.split(None, 1)
-    first = parts[0] if parts else "Monica"
-    last = parts[1] if len(parts) > 1 else ""
-    return {
-        "company": "",
-        "firstName": first,
-        "lastName": last,
-        "address": str(getattr(settings, "PCM_RETURN_LINE1", "") or ""),
-        "address2": str(getattr(settings, "PCM_RETURN_LINE2", "") or ""),
-        "city": str(getattr(settings, "PCM_RETURN_CITY", "") or ""),
-        "state": str(getattr(settings, "PCM_RETURN_STATE", "") or ""),
-        "zipCode": str(getattr(settings, "PCM_RETURN_ZIP", "") or ""),
+    site_first = parts[0] if parts else ""
+    site_last = parts[1] if len(parts) > 1 else ""
+
+    address = {
+        "company": str(data.get("company") or "").strip(),
+        "firstName": str(
+            data.get("firstName") or data.get("first_name") or site_first or ""
+        ).strip(),
+        "lastName": str(
+            data.get("lastName") or data.get("last_name") or site_last or ""
+        ).strip(),
+        "address": str(
+            data.get("address")
+            or data.get("line1")
+            or getattr(settings, "PCM_RETURN_LINE1", "")
+            or ""
+        ).strip(),
+        # PCM treats blank address2 oddly; space matches recipient payload.
+        "address2": str(
+            data.get("address2")
+            or data.get("line2")
+            or getattr(settings, "PCM_RETURN_LINE2", "")
+            or ""
+        ).strip()
+        or " ",
+        "city": str(
+            data.get("city") or getattr(settings, "PCM_RETURN_CITY", "") or ""
+        ).strip(),
+        "state": str(
+            data.get("state") or getattr(settings, "PCM_RETURN_STATE", "") or ""
+        ).strip(),
+        "zipCode": str(
+            data.get("zipCode")
+            or data.get("zip")
+            or getattr(settings, "PCM_RETURN_ZIP", "")
+            or ""
+        ).strip(),
     }
 
+    missing = [
+        field
+        for field in ("firstName", "address", "city", "state", "zipCode")
+        if not address.get(field, "").strip()
+    ]
+    if missing:
+        raise PcmApiError(
+            "PCM return address incomplete (missing "
+            + ", ".join(missing)
+            + "). Set PCM_RETURN_ADDRESS JSON with firstName, lastName, "
+            "address, city, state, zipCode "
+            "(or PCM_RETURN_LINE1 / CITY / STATE / ZIP)."
+        )
+    return address
+
 
 def contact_to_pcm_recipient(contact, *, ext_ref: str) -> dict[str, str]:
     address = contact.postal_address or {}
diff --git a/site/messaging/tests.py b/site/messaging/tests.py
index 4673970..1cd18fd 100644
--- a/site/messaging/tests.py
+++ b/site/messaging/tests.py
@@ -1079,6 +1079,34 @@ class PcmAuthTests(TestCase):
                 pcm_mod.login(force=True)
         self.assertIn("PCM_API_SECRET", str(ctx.exception))
 
+    def test_return_address_requires_street_fields(self):
+        from messaging.providers.postcard import pcm as pcm_mod
+
+        with self.settings(
+            SITE_NAME="Monica Dhillon",
+            PCM_RETURN_ADDRESS="",
+            PCM_RETURN_LINE1="",
+            PCM_RETURN_CITY="",
+            PCM_RETURN_STATE="",
+            PCM_RETURN_ZIP="",
+        ):
+            with self.assertRaises(pcm_mod.PcmApiError) as ctx:
+                pcm_mod.return_address_from_settings()
+        self.assertIn("PCM return address incomplete", str(ctx.exception))
+
+    def test_return_address_from_json(self):
+        from messaging.providers.postcard import pcm as pcm_mod
+
+        with self.settings(
+            PCM_RETURN_ADDRESS=(
+                '{"firstName":"Mo","lastName":"D","address":"1 Main",'
+                '"city":"Naperville","state":"IL","zipCode":"60540"}'
+            ),
+        ):
+            addr = pcm_mod.return_address_from_settings()
+        self.assertEqual(addr["address"], "1 Main")
+        self.assertEqual(addr["zipCode"], "60540")
+
 
 class PostcardAddressDefaultConsentTests(TestCase):
     def test_address_without_consent_is_postcard_eligible(self):