diff --git a/src/govoplan_postbox/backend/db/models.py b/src/govoplan_postbox/backend/db/models.py
index 9f02229..8357fc1 100644
--- a/src/govoplan_postbox/backend/db/models.py
+++ b/src/govoplan_postbox/backend/db/models.py
@@ -482,6 +482,11 @@ class PostboxMessage(Base, TimestampMixin):
         default=list,
         nullable=False,
     )
+    external_recipient_tokens: Mapped[list[dict[str, Any]]] = mapped_column(
+        JSON,
+        default=list,
+        nullable=False,
+    )
     delivered_at: Mapped[datetime] = mapped_column(
         DateTime(timezone=True),
         nullable=False,
diff --git a/src/govoplan_postbox/backend/migrations/versions/a6d9e1f4c8b3_v013_external_recipient_tokens.py b/src/govoplan_postbox/backend/migrations/versions/a6d9e1f4c8b3_v013_external_recipient_tokens.py
new file mode 100644
index 0000000..fccb788
--- /dev/null
+++ b/src/govoplan_postbox/backend/migrations/versions/a6d9e1f4c8b3_v013_external_recipient_tokens.py
@@ -0,0 +1,33 @@
+"""v0.1.3 external recipient token state
+
+Revision ID: a6d9e1f4c8b3
+Revises: f5c8d0e3b7a2
+Create Date: 2026-07-31 18:00:00.000000
+"""
+from __future__ import annotations
+
+from alembic import op
+import sqlalchemy as sa
+
+
+revision = "a6d9e1f4c8b3"
+down_revision = "f5c8d0e3b7a2"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    with op.batch_alter_table("postbox_messages") as batch_op:
+        batch_op.add_column(
+            sa.Column(
+                "external_recipient_tokens",
+                sa.JSON(),
+                nullable=False,
+                server_default=sa.text("'[]'"),
+            )
+        )
+
+
+def downgrade() -> None:
+    with op.batch_alter_table("postbox_messages") as batch_op:
+        batch_op.drop_column("external_recipient_tokens")
diff --git a/src/govoplan_postbox/backend/router.py b/src/govoplan_postbox/backend/router.py
index 8b8ed3b..6304008 100644
--- a/src/govoplan_postbox/backend/router.py
+++ b/src/govoplan_postbox/backend/router.py
@@ -17,9 +17,11 @@ from govoplan_core.core.postbox import (
     PostboxActorRef,
     PostboxAttachmentRef,
     PostboxDeliveryRequest,
+    PostboxExternalRecipientTokenRef,
     PostboxMessageAuthoringRequest,
     PostboxParticipantRef,
     PostboxTargetRef,
+    PostboxWrappedKeyRef,
 )
 from govoplan_core.db.session import get_session
 from govoplan_postbox.backend.manifest import (
@@ -103,7 +105,15 @@ def _actor(
         TEMPLATE_ADMIN_SCOPE,
     ):
         actions.add("administer")
-    selected = assignment_context_id
+    if (
+        assignment_context_id is not None
+        and assignment_context_id not in principal.function_assignment_ids
+    ):
+        raise HTTPException(
+            status_code=status.HTTP_403_FORBIDDEN,
+            detail="The selected assignment context is not active for this principal.",
+        )
+    selected = assignment_context_id or principal.acting_assignment_id
     if selected is None and len(principal.function_assignment_ids) == 1:
         selected = next(iter(principal.function_assignment_ids))
     classifications = {"public", "internal"}
@@ -542,6 +552,16 @@ def api_deliver_to_postbox(
             for attachment in payload.attachments
         ),
         expires_at=payload.expires_at,
+        ciphertext_ref=payload.ciphertext_ref,
+        signed_manifest_ref=payload.signed_manifest_ref,
+        wrapped_keys=tuple(
+            PostboxWrappedKeyRef(**item.model_dump())
+            for item in payload.wrapped_keys
+        ),
+        external_recipient_tokens=tuple(
+            PostboxExternalRecipientTokenRef(**item.model_dump())
+            for item in payload.external_recipient_tokens
+        ),
         metadata=payload.metadata,
     )
     try:
diff --git a/src/govoplan_postbox/backend/schemas.py b/src/govoplan_postbox/backend/schemas.py
index 3833091..e198abd 100644
--- a/src/govoplan_postbox/backend/schemas.py
+++ b/src/govoplan_postbox/backend/schemas.py
@@ -75,6 +75,26 @@ class PostboxAttachmentPayload(BaseModel):
     metadata: dict[str, Any] = Field(default_factory=dict)
 
 
+class PostboxWrappedKeyPayload(BaseModel):
+    recipient_type: str = Field(min_length=1, max_length=50)
+    recipient_id: str = Field(min_length=1, max_length=255)
+    key_epoch: int = Field(ge=1)
+    wrapped_key_ref: str = Field(min_length=1, max_length=2000)
+    algorithm: str | None = Field(default=None, max_length=100)
+    metadata: dict[str, Any] = Field(default_factory=dict)
+
+
+class PostboxExternalRecipientTokenPayload(BaseModel):
+    token_id: str = Field(min_length=1, max_length=255)
+    state: Literal["pending", "available", "fetched", "expired", "revoked"]
+    expires_at: datetime | None = None
+    one_time: bool = False
+    key_fetched_at: datetime | None = None
+    revoked_at: datetime | None = None
+    assurance_profile: str | None = Field(default=None, max_length=100)
+    metadata: dict[str, Any] = Field(default_factory=dict)
+
+
 class PostboxMessageItem(BaseModel):
     id: str
     tenant_id: str
@@ -99,6 +119,10 @@ class PostboxMessageItem(BaseModel):
     key_epoch: int
     ciphertext_ref: str | None = None
     signed_manifest_ref: str | None = None
+    wrapped_keys: list[PostboxWrappedKeyPayload] = Field(default_factory=list)
+    external_recipient_tokens: list[PostboxExternalRecipientTokenPayload] = Field(
+        default_factory=list
+    )
     participants: list[PostboxParticipantPayload] = Field(default_factory=list)
     attachments: list[PostboxAttachmentPayload] = Field(default_factory=list)
     metadata: dict[str, Any] = Field(default_factory=dict)
@@ -165,6 +189,12 @@ class PostboxDeliveryCreateRequest(BaseModel):
     participants: list[PostboxParticipantPayload] = Field(default_factory=list)
     attachments: list[PostboxAttachmentPayload] = Field(default_factory=list)
     expires_at: datetime | None = None
+    ciphertext_ref: str | None = Field(default=None, max_length=1000)
+    signed_manifest_ref: str | None = Field(default=None, max_length=1000)
+    wrapped_keys: list[PostboxWrappedKeyPayload] = Field(default_factory=list)
+    external_recipient_tokens: list[PostboxExternalRecipientTokenPayload] = Field(
+        default_factory=list
+    )
     metadata: dict[str, Any] = Field(default_factory=dict)
 
 
diff --git a/src/govoplan_postbox/backend/service.py b/src/govoplan_postbox/backend/service.py
index acd7e68..7b6b3b2 100644
--- a/src/govoplan_postbox/backend/service.py
+++ b/src/govoplan_postbox/backend/service.py
@@ -6,6 +6,7 @@ import logging
 import re
 from collections import Counter
 from collections.abc import Mapping, Sequence
+from dataclasses import asdict
 from datetime import datetime, timedelta, timezone
 from typing import Any, Literal
 
@@ -58,6 +59,7 @@ from govoplan_core.core.postbox import (
     PostboxDeliveryResult,
     PostboxDeliveryTemplateRef,
     PostboxDirectoryEntryRef,
+    PostboxExternalRecipientTokenRef,
     PostboxMessageAvailability,
     PostboxMessageAuthoringRequest,
     PostboxMessageRef,
@@ -66,6 +68,7 @@ from govoplan_core.core.postbox import (
     PostboxOrganizationUnitTargetRef,
     PostboxParticipantRef,
     PostboxTargetRef,
+    PostboxWrappedKeyRef,
     normalize_postbox_classification,
     postbox_classification_allows,
 )
@@ -127,6 +130,34 @@ def _mapping(value: Mapping[str, object] | None) -> dict[str, object]:
     return dict(value or {})
 
 
+def _optional_datetime(value: object) -> datetime | None:
+    if isinstance(value, datetime):
+        return value
+    if isinstance(value, str) and value:
+        try:
+            return datetime.fromisoformat(value)
+        except ValueError:
+            return None
+    return None
+
+
+def _external_token_record(
+    token: PostboxExternalRecipientTokenRef,
+) -> dict[str, object]:
+    return {
+        "token_id": token.token_id,
+        "state": token.state,
+        "expires_at": token.expires_at.isoformat() if token.expires_at else None,
+        "one_time": token.one_time,
+        "key_fetched_at": (
+            token.key_fetched_at.isoformat() if token.key_fetched_at else None
+        ),
+        "revoked_at": token.revoked_at.isoformat() if token.revoked_at else None,
+        "assurance_profile": token.assurance_profile,
+        "metadata": dict(token.metadata),
+    }
+
+
 def _authoring_digest(
     request: PostboxMessageAuthoringRequest,
     *,
@@ -1157,6 +1188,13 @@ class PostboxService:
             producer_resource_id=request.producer_resource_id,
             encryption_profile=postbox.encryption_profile,
             key_epoch=postbox.key_epoch,
+            ciphertext_ref=request.ciphertext_ref,
+            signed_manifest_ref=request.signed_manifest_ref,
+            wrapped_keys=[asdict(item) for item in request.wrapped_keys],
+            external_recipient_tokens=[
+                _external_token_record(item)
+                for item in request.external_recipient_tokens
+            ],
             delivered_at=now,
             expires_at=request.expires_at,
             metadata_=_mapping(request.metadata),
@@ -1820,6 +1858,12 @@ class PostboxService:
             producer_resource_id=source_message.producer_resource_id,
             encryption_profile=target_postbox.encryption_profile,
             key_epoch=target_postbox.key_epoch,
+            ciphertext_ref=source_message.ciphertext_ref,
+            signed_manifest_ref=source_message.signed_manifest_ref,
+            wrapped_keys=list(source_message.wrapped_keys or []),
+            external_recipient_tokens=list(
+                source_message.external_recipient_tokens or []
+            ),
             delivered_at=delivered_at,
             expires_at=source_message.expires_at,
             retention_hold_until=source_message.retention_hold_until,
@@ -3734,6 +3778,38 @@ class PostboxService:
             key_epoch=message.key_epoch,
             ciphertext_ref=message.ciphertext_ref,
             signed_manifest_ref=message.signed_manifest_ref,
+            wrapped_keys=tuple(
+                PostboxWrappedKeyRef(
+                    recipient_type=str(item.get("recipient_type") or "unknown"),
+                    recipient_id=str(item.get("recipient_id") or "unknown"),
+                    key_epoch=int(item.get("key_epoch") or message.key_epoch),
+                    wrapped_key_ref=str(item.get("wrapped_key_ref") or ""),
+                    algorithm=(
+                        str(item["algorithm"]) if item.get("algorithm") else None
+                    ),
+                    metadata=_mapping(item.get("metadata")),
+                )
+                for item in message.wrapped_keys or []
+                if isinstance(item, Mapping) and item.get("wrapped_key_ref")
+            ),
+            external_recipient_tokens=tuple(
+                PostboxExternalRecipientTokenRef(
+                    token_id=str(item.get("token_id") or ""),
+                    state=str(item.get("state") or "pending"),
+                    expires_at=_optional_datetime(item.get("expires_at")),
+                    one_time=bool(item.get("one_time", False)),
+                    key_fetched_at=_optional_datetime(item.get("key_fetched_at")),
+                    revoked_at=_optional_datetime(item.get("revoked_at")),
+                    assurance_profile=(
+                        str(item["assurance_profile"])
+                        if item.get("assurance_profile")
+                        else None
+                    ),
+                    metadata=_mapping(item.get("metadata")),
+                )
+                for item in message.external_recipient_tokens or []
+                if isinstance(item, Mapping) and item.get("token_id")
+            ),
             participants=tuple(
                 PostboxParticipantRef(
                     kind=item.kind,
diff --git a/tests/test_migration.py b/tests/test_migration.py
index d36ded6..cb086d9 100644
--- a/tests/test_migration.py
+++ b/tests/test_migration.py
@@ -22,6 +22,10 @@ class PostboxMigrationTests(unittest.TestCase):
             "govoplan_postbox.backend.migrations.versions."
             "f5c8d0e3b7a2_v012_authoring_and_occ"
         )
+        envelope_migration = importlib.import_module(
+            "govoplan_postbox.backend.migrations.versions."
+            "a6d9e1f4c8b3_v013_external_recipient_tokens"
+        )
         engine = create_engine("sqlite:///:memory:")
         try:
             with engine.begin() as connection:
@@ -29,13 +33,16 @@ class PostboxMigrationTests(unittest.TestCase):
                 original = migration.op
                 route_original = route_migration.op
                 occ_original = occ_migration.op
+                envelope_original = envelope_migration.op
                 migration.op = operations
                 route_migration.op = operations
                 occ_migration.op = operations
+                envelope_migration.op = operations
                 try:
                     migration.upgrade()
                     route_migration.upgrade()
                     occ_migration.upgrade()
+                    envelope_migration.upgrade()
                     tables = set(inspect(connection).get_table_names())
                     self.assertIn("postboxes", tables)
                     self.assertIn("postbox_messages", tables)
@@ -52,6 +59,7 @@ class PostboxMigrationTests(unittest.TestCase):
                             "ciphertext_ref",
                             "signed_manifest_ref",
                             "wrapped_keys",
+                            "external_recipient_tokens",
                             "key_epoch",
                             "expires_at",
                             "withdrawn_at",
@@ -83,6 +91,7 @@ class PostboxMigrationTests(unittest.TestCase):
                             route_columns
                         )
                     )
+                    envelope_migration.downgrade()
                     occ_migration.downgrade()
                     route_migration.downgrade()
                     migration.downgrade()
@@ -97,6 +106,7 @@ class PostboxMigrationTests(unittest.TestCase):
                     migration.op = original
                     route_migration.op = route_original
                     occ_migration.op = occ_original
+                    envelope_migration.op = envelope_original
         finally:
             engine.dispose()
 
diff --git a/tests/test_router.py b/tests/test_router.py
index 1679fd4..2320d34 100644
--- a/tests/test_router.py
+++ b/tests/test_router.py
@@ -241,6 +241,15 @@ class PostboxRouterTests(unittest.TestCase):
         self.patch.stop()
         self.engine.dispose()
 
+    def test_assignment_context_override_must_belong_to_principal(self) -> None:
+        response = self.client.get(
+            "/api/v1/postbox/directory",
+            params={"assignment_context_id": "assignment-not-granted"},
+        )
+
+        self.assertEqual(response.status_code, 403)
+        self.assertIn("not active for this principal", response.text)
+
     def test_directory_delivery_message_and_receipt_round_trip(self) -> None:
         directory = self.client.get("/api/v1/postbox/directory")
         self.assertEqual(200, directory.status_code, directory.text)
diff --git a/tests/test_service.py b/tests/test_service.py
index 40f636e..21e4228 100644
--- a/tests/test_service.py
+++ b/tests/test_service.py
@@ -29,7 +29,9 @@ from govoplan_core.core.organizations import (
 from govoplan_core.core.postbox import (
     PostboxActorRef,
     PostboxDeliveryRequest,
+    PostboxExternalRecipientTokenRef,
     PostboxTargetRef,
+    PostboxWrappedKeyRef,
 )
 from govoplan_core.db.base import Base
 from govoplan_core.security.time import utc_now
@@ -1173,6 +1175,67 @@ class PostboxServiceTests(unittest.TestCase):
             self.assertFalse(summaries[expired.delivery_id].currently_readable)
             self.assertEqual(1, summaries[expired.delivery_id].expired_message_count)
 
+    def test_encrypted_envelope_and_external_grant_state_cross_capability(self) -> None:
+        self.idm.assignments.append(self.assignment)
+        expires_at = utc_now() + timedelta(days=1)
+        with Session(self.engine) as session:
+            postbox = self._create_exact(session)
+            delivered = self.service.deliver(
+                session,
+                PostboxDeliveryRequest(
+                    tenant_id="tenant-1",
+                    target=PostboxTargetRef(postbox_id=postbox.id),
+                    producer_module="campaigns",
+                    producer_resource_type="campaign_recipient",
+                    producer_resource_id="recipient-encrypted",
+                    idempotency_key="encrypted-message",
+                    subject="Encrypted decision",
+                    ciphertext_ref="files:ciphertext-1",
+                    signed_manifest_ref="files:manifest-1",
+                    wrapped_keys=(
+                        PostboxWrappedKeyRef(
+                            recipient_type="function_postbox",
+                            recipient_id=postbox.id,
+                            key_epoch=postbox.key_epoch,
+                            wrapped_key_ref="trust:wrapped-key-1",
+                            algorithm="HPKE-v1",
+                        ),
+                    ),
+                    external_recipient_tokens=(
+                        PostboxExternalRecipientTokenRef(
+                            token_id="grant-1",
+                            state="available",
+                            expires_at=expires_at,
+                            one_time=True,
+                            assurance_profile="email-otp",
+                        ),
+                    ),
+                ),
+            )
+
+            message = self.service.get_message(
+                session,
+                tenant_id="tenant-1",
+                message_id=delivered.message_id,
+                actor=self.actor,
+            )
+
+            assert message is not None
+            self.assertEqual("files:ciphertext-1", message.ciphertext_ref)
+            self.assertEqual(
+                "trust:wrapped-key-1",
+                message.wrapped_keys[0].wrapped_key_ref,
+            )
+            self.assertEqual("grant-1", message.external_recipient_tokens[0].token_id)
+            self.assertEqual("available", message.external_recipient_tokens[0].state)
+            assert message.external_recipient_tokens[0].expires_at is not None
+            self.assertEqual(
+                expires_at.replace(microsecond=0),
+                message.external_recipient_tokens[0].expires_at.replace(
+                    microsecond=0
+                ),
+            )
+
     def test_hierarchy_linked_copy_snapshots_path_and_independent_state(
         self,
     ) -> None:
diff --git a/webui/src/api/postbox.ts b/webui/src/api/postbox.ts
index d5224b2..c3a4136 100644
--- a/webui/src/api/postbox.ts
+++ b/webui/src/api/postbox.ts
@@ -86,6 +86,24 @@ export type PostboxMessage = {
   key_epoch: number;
   ciphertext_ref?: string | null;
   signed_manifest_ref?: string | null;
+  wrapped_keys: Array<{
+    recipient_type: string;
+    recipient_id: string;
+    key_epoch: number;
+    wrapped_key_ref: string;
+    algorithm?: string | null;
+    metadata: Record<string, unknown>;
+  }>;
+  external_recipient_tokens: Array<{
+    token_id: string;
+    state: "pending" | "available" | "fetched" | "expired" | "revoked";
+    expires_at?: string | null;
+    one_time: boolean;
+    key_fetched_at?: string | null;
+    revoked_at?: string | null;
+    assurance_profile?: string | null;
+    metadata: Record<string, unknown>;
+  }>;
   participants: PostboxParticipant[];
   attachments: PostboxAttachment[];
   metadata: Record<string, unknown>;
diff --git a/webui/src/features/postbox/PostboxPage.tsx b/webui/src/features/postbox/PostboxPage.tsx
index 7d61293..0144db7 100644
--- a/webui/src/features/postbox/PostboxPage.tsx
+++ b/webui/src/features/postbox/PostboxPage.tsx
@@ -999,7 +999,7 @@ function MessageDetail({
           resetKey={`${message.id}:${message.availability}`}
         >
           {message.availability === "withdrawn"
-            ? "This message was withdrawn. Its audit metadata remains visible, but its content and actions are unavailable."
+            ? "This message was withdrawn. Future access is blocked and audit metadata remains visible. Plaintext already decrypted, copied, exported, or printed cannot be retracted."
             : "This message has expired. Its audit metadata remains visible, but its content and actions are unavailable."}
         </DismissibleAlert>
       ) : null}
@@ -1026,6 +1026,12 @@ function MessageDetail({
           <div><dt>Address</dt><dd>{postbox?.address || "Not loaded"}</dd></div>
           <div><dt>Producer</dt><dd>{producerLabel(message)}</dd></div>
           <div><dt>Encryption profile</dt><dd>{message.encryption_profile} · epoch {message.key_epoch}</dd></div>
+          {message.wrapped_keys.length ? (
+            <div><dt>Key envelopes</dt><dd>{message.wrapped_keys.length}</dd></div>
+          ) : null}
+          {message.external_recipient_tokens.length ? (
+            <div><dt>External grants</dt><dd>{message.external_recipient_tokens.length}</dd></div>
+          ) : null}
         </dl>
       </section>
       <section className="postbox-body">