diff --git a/service/src/main/java/org/whispersystems/textsecuregcm/controllers/MessageController.java b/service/src/main/java/org/whispersystems/textsecuregcm/controllers/MessageController.java
index 0c1ee9e75..37e2999c2 100644
--- a/service/src/main/java/org/whispersystems/textsecuregcm/controllers/MessageController.java
+++ b/service/src/main/java/org/whispersystems/textsecuregcm/controllers/MessageController.java
@@ -38,6 +38,7 @@ import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.function.Function;
 import java.util.stream.Collectors;
+import java.util.stream.Stream;
 import javax.validation.Valid;
 import javax.ws.rs.Consumes;
 import javax.ws.rs.DELETE;
@@ -62,6 +63,7 @@ import org.whispersystems.textsecuregcm.auth.CombinedUnidentifiedSenderAccessKey
 import org.whispersystems.textsecuregcm.auth.OptionalAccess;
 import org.whispersystems.textsecuregcm.configuration.dynamic.DynamicMessageRateConfiguration;
 import org.whispersystems.textsecuregcm.entities.AccountMismatchedDevices;
+import org.whispersystems.textsecuregcm.entities.AccountStaleDevices;
 import org.whispersystems.textsecuregcm.entities.IncomingMessage;
 import org.whispersystems.textsecuregcm.entities.IncomingMessageList;
 import org.whispersystems.textsecuregcm.entities.MessageProtos.Envelope;
@@ -94,6 +96,7 @@ import org.whispersystems.textsecuregcm.storage.MessagesManager;
 import org.whispersystems.textsecuregcm.storage.ReportMessageManager;
 import org.whispersystems.textsecuregcm.util.Constants;
 import org.whispersystems.textsecuregcm.util.ForwardedIpUtil;
+import org.whispersystems.textsecuregcm.util.Pair;
 import org.whispersystems.textsecuregcm.util.Util;
 import org.whispersystems.textsecuregcm.util.ua.UnrecognizedUserAgentException;
 import org.whispersystems.textsecuregcm.util.ua.UserAgentUtil;
@@ -360,16 +363,23 @@ public class MessageController {
     checkAccessKeys(accessKeys, uuidToAccountMap);
 
     List<AccountMismatchedDevices> accountMismatchedDevices = new ArrayList<>();
+    List<AccountStaleDevices> accountStaleDevices = new ArrayList<>();
     for (Account account : uuidToAccountMap.values()) {
       Set<Long> deviceIds = Arrays.stream(multiRecipientMessage.getRecipients())
           .filter(recipient -> recipient.getUuid().equals(account.getUuid()))
           .map(Recipient::getDeviceId)
           .collect(Collectors.toSet());
+      Stream<Pair<Long, Integer>> deviceIdAndRegistrationIdStream = Arrays.stream(multiRecipientMessage.getRecipients())
+          .filter(recipient -> recipient.getUuid().equals(account.getUuid()))
+          .map(recipient -> new Pair<>(recipient.getDeviceId(), recipient.getRegistrationId()));
       try {
         validateCompleteDeviceList(account, deviceIds, false);
+        validateRegistrationIds(account, deviceIdAndRegistrationIdStream);
       } catch (MismatchedDevicesException e) {
         accountMismatchedDevices.add(new AccountMismatchedDevices(account.getUuid(),
             new MismatchedDevices(e.getMissingDevices(), e.getExtraDevices())));
+      } catch (StaleDevicesException e) {
+        accountStaleDevices.add(new AccountStaleDevices(account.getUuid(), new StaleDevices(e.getStaleDevices())));
       }
     }
     if (!accountMismatchedDevices.isEmpty()) {
@@ -379,6 +389,13 @@ public class MessageController {
           .entity(accountMismatchedDevices)
           .build();
     }
+    if (!accountStaleDevices.isEmpty()) {
+      return Response
+          .status(410)
+          .type(MediaType.APPLICATION_JSON)
+          .entity(accountStaleDevices)
+          .build();
+    }
 
     List<Tag> tags = List.of(
         UserAgentTagUtil.getPlatformTag(userAgent),
@@ -639,20 +656,23 @@ public class MessageController {
   }
 
   private void validateRegistrationIds(Account account, List<IncomingMessage> messages)
-      throws StaleDevicesException
-  {
-    List<Long> staleDevices = new LinkedList<>();
+      throws StaleDevicesException {
+    final Stream<Pair<Long, Integer>> deviceIdAndRegistrationIdStream = messages
+        .stream()
+        .map(message -> new Pair<>(message.getDestinationDeviceId(), message.getDestinationRegistrationId()));
+    validateRegistrationIds(account, deviceIdAndRegistrationIdStream);
+  }
 
-    for (IncomingMessage message : messages) {
-      Optional<Device> device = account.getDevice(message.getDestinationDeviceId());
-
-      if (device.isPresent() &&
-          message.getDestinationRegistrationId() > 0 &&
-          message.getDestinationRegistrationId() != device.get().getRegistrationId())
-      {
-        staleDevices.add(device.get().getId());
-      }
-    }
+  private void validateRegistrationIds(Account account, Stream<Pair<Long, Integer>> deviceIdAndRegistrationIdStream)
+      throws StaleDevicesException {
+    final List<Long> staleDevices = deviceIdAndRegistrationIdStream
+        .filter(deviceIdAndRegistrationId -> deviceIdAndRegistrationId.second() > 0)
+        .filter(deviceIdAndRegistrationId -> {
+          Optional<Device> device = account.getDevice(deviceIdAndRegistrationId.first());
+          return device.isPresent() && deviceIdAndRegistrationId.second() != device.get().getRegistrationId();
+        })
+        .map(Pair::first)
+        .collect(Collectors.toList());
 
     if (!staleDevices.isEmpty()) {
       throw new StaleDevicesException(staleDevices);
diff --git a/service/src/main/java/org/whispersystems/textsecuregcm/entities/AccountStaleDevices.java b/service/src/main/java/org/whispersystems/textsecuregcm/entities/AccountStaleDevices.java
new file mode 100644
index 000000000..35d818ea0
--- /dev/null
+++ b/service/src/main/java/org/whispersystems/textsecuregcm/entities/AccountStaleDevices.java
@@ -0,0 +1,22 @@
+/*
+ * Copyright 2021 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.whispersystems.textsecuregcm.entities;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+import java.util.UUID;
+
+public class AccountStaleDevices {
+  @JsonProperty
+  public final UUID uuid;
+
+  @JsonProperty
+  public final StaleDevices devices;
+
+  public AccountStaleDevices(final UUID uuid, final StaleDevices devices) {
+    this.uuid = uuid;
+    this.devices = devices;
+  }
+}
diff --git a/service/src/main/java/org/whispersystems/textsecuregcm/entities/MultiRecipientMessage.java b/service/src/main/java/org/whispersystems/textsecuregcm/entities/MultiRecipientMessage.java
index 73ac76104..564d007f4 100644
--- a/service/src/main/java/org/whispersystems/textsecuregcm/entities/MultiRecipientMessage.java
+++ b/service/src/main/java/org/whispersystems/textsecuregcm/entities/MultiRecipientMessage.java
@@ -6,6 +6,8 @@
 package org.whispersystems.textsecuregcm.entities;
 
 import java.util.UUID;
+import javax.validation.Valid;
+import javax.validation.constraints.Max;
 import javax.validation.constraints.Min;
 import javax.validation.constraints.NotNull;
 import javax.validation.constraints.Size;
@@ -21,13 +23,18 @@ public class MultiRecipientMessage {
     @Min(1)
     private final long deviceId;
 
+    @Min(0)
+    @Max(65535)
+    private final int registrationId;
+
     @Size(min = 48, max = 48)
     @NotNull
     private final byte[] perRecipientKeyMaterial;
 
-    public Recipient(UUID uuid, long deviceId, byte[] perRecipientKeyMaterial) {
+    public Recipient(UUID uuid, long deviceId, int registrationId, byte[] perRecipientKeyMaterial) {
       this.uuid = uuid;
       this.deviceId = deviceId;
+      this.registrationId = registrationId;
       this.perRecipientKeyMaterial = perRecipientKeyMaterial;
     }
 
@@ -39,6 +46,10 @@ public class MultiRecipientMessage {
       return deviceId;
     }
 
+    public int getRegistrationId() {
+      return registrationId;
+    }
+
     public byte[] getPerRecipientKeyMaterial() {
       return perRecipientKeyMaterial;
     }
@@ -46,6 +57,7 @@ public class MultiRecipientMessage {
 
   @NotNull
   @Size(min = 1, max = MultiRecipientMessageProvider.MAX_RECIPIENT_COUNT)
+  @Valid
   private final Recipient[] recipients;
 
   @NotNull
diff --git a/service/src/main/java/org/whispersystems/textsecuregcm/providers/MultiRecipientMessageProvider.java b/service/src/main/java/org/whispersystems/textsecuregcm/providers/MultiRecipientMessageProvider.java
index 1f6ec12ed..da9029899 100644
--- a/service/src/main/java/org/whispersystems/textsecuregcm/providers/MultiRecipientMessageProvider.java
+++ b/service/src/main/java/org/whispersystems/textsecuregcm/providers/MultiRecipientMessageProvider.java
@@ -54,11 +54,12 @@ public class MultiRecipientMessageProvider implements MessageBodyReader<MultiRec
     for (int i = 0; i < Math.toIntExact(count); i++) {
       UUID uuid = readUuid(entityStream);
       long deviceId = readVarint(entityStream);
+      int registrationId = readU16(entityStream);
       byte[] perRecipientKeyMaterial = entityStream.readNBytes(48);
       if (perRecipientKeyMaterial.length != 48) {
         throw new IOException("Failed to read expected number of key material bytes for a recipient");
       }
-      recipients[i] = new MultiRecipientMessage.Recipient(uuid, deviceId, perRecipientKeyMaterial);
+      recipients[i] = new MultiRecipientMessage.Recipient(uuid, deviceId, registrationId, perRecipientKeyMaterial);
     }
 
     // caller is responsible for checking that the entity stream is at EOF when we return; if there are more bytes than
@@ -126,4 +127,20 @@ public class MultiRecipientMessageProvider implements MessageBodyReader<MultiRec
     }
     return result;
   }
+
+  /**
+   * Reads two bytes with most significant byte first. Treats the value as unsigned so the range returned is
+   * {@code [0, 65535]}.
+   */
+  private int readU16(InputStream stream) throws IOException {
+    int b1 = stream.read();
+    if (b1 == -1) {
+      throw new IOException("Missing byte 1 of U16");
+    }
+    int b2 = stream.read();
+    if (b2 == -1) {
+      throw new IOException("Missing byte 2 of U16");
+    }
+    return (b1 << 8) | b2;
+  }
 }