diff --git a/lib/api/route/messages.dart b/lib/api/route/messages.dart
index 5226444b06..27a12c3ae0 100644
--- a/lib/api/route/messages.dart
+++ b/lib/api/route/messages.dart
@@ -177,6 +177,7 @@ Future<SendMessageResult> sendMessage(
   required String content,
   String? queueId,
   String? localId,
+  bool? readBySender,
 }) {
   final supportsTypeDirect = connection.zulipFeatureLevel! >= 174; // TODO(server-7)
   return connection.post('sendMessage', SendMessageResult.fromJson, 'messages', {
@@ -191,8 +192,9 @@ Future<SendMessageResult> sendMessage(
       throw Exception('impossible destination') // TODO(dart-3) show this statically
     ),
     'content': RawParameter(content),
-    if (queueId != null) 'queue_id': queueId,
-    if (localId != null) 'local_id': localId,
+    if (queueId != null) 'queue_id': queueId, // TODO should this use RawParameter?
+    if (localId != null) 'local_id': localId, // TODO should this use RawParameter?
+    if (readBySender != null) 'read_by_sender': readBySender,
   });
 }
 
diff --git a/lib/model/store.dart b/lib/model/store.dart
index ea4833ab62..39a9320552 100644
--- a/lib/model/store.dart
+++ b/lib/model/store.dart
@@ -380,7 +380,11 @@ class PerAccountStore extends ChangeNotifier with StreamStore {
   Future<void> sendMessage({required MessageDestination destination, required String content}) {
     // TODO implement outbox; see design at
     //   https://chat.zulip.org/#narrow/stream/243-mobile-team/topic/.23M3881.20Sending.20outbox.20messages.20is.20fraught.20with.20issues/near/1405739
-    return _apiSendMessage(connection, destination: destination, content: content);
+    return _apiSendMessage(connection,
+      destination: destination,
+      content: content,
+      readBySender: true,
+    );
   }
 
   static List<CustomProfileField> _sortCustomProfileFields(List<CustomProfileField> initialCustomProfileFields) {
diff --git a/test/api/route/messages_test.dart b/test/api/route/messages_test.dart
index 9e3975ca42..221b53ba37 100644
--- a/test/api/route/messages_test.dart
+++ b/test/api/route/messages_test.dart
@@ -300,11 +300,15 @@ void main() {
       FakeApiConnection connection, {
       required MessageDestination destination,
       required String content,
+      String? queueId,
+      String? localId,
+      bool? readBySender,
       required Map<String, String> expectedBodyFields,
     }) async {
       connection.prepare(json: SendMessageResult(id: 42).toJson());
       final result = await sendMessage(connection,
-        destination: destination, content: content);
+        destination: destination, content: content,
+        queueId: queueId, localId: localId, readBySender: readBySender);
       check(result).id.equals(42);
       check(connection.lastRequest).isA<http.Request>()
         ..method.equals('POST')
@@ -312,6 +316,25 @@ void main() {
         ..bodyFields.deepEquals(expectedBodyFields);
     }
 
+    test('smoke', () {
+      return FakeApiConnection.with_((connection) async {
+        await checkSendMessage(connection,
+          destination: StreamDestination(streamId, topic), content: content,
+          queueId: 'abc:123',
+          localId: '456',
+          readBySender: true,
+          expectedBodyFields: {
+            'type': 'stream',
+            'to': streamId.toString(),
+            'topic': topic,
+            'content': content,
+            'queue_id': '"abc:123"',
+            'local_id': '"456"',
+            'read_by_sender': 'true',
+          });
+      });
+    });
+
     test('to stream', () {
       return FakeApiConnection.with_((connection) async {
         await checkSendMessage(connection,
diff --git a/test/model/store_test.dart b/test/model/store_test.dart
index a13bdc9b2b..07ce1beedf 100644
--- a/test/model/store_test.dart
+++ b/test/model/store_test.dart
@@ -4,6 +4,7 @@ import 'package:checks/checks.dart';
 import 'package:flutter/foundation.dart';
 import 'package:http/http.dart' as http;
 import 'package:test/scaffolding.dart';
+import 'package:zulip/api/route/messages.dart';
 import 'package:zulip/model/store.dart';
 import 'package:zulip/notifications.dart';
 
@@ -108,6 +109,28 @@ void main() {
     check(completers(1)).length.equals(1);
   });
 
+  group('PerAccountStore.sendMessage', () {
+    test('smoke', () async {
+      final store = eg.store();
+      final connection = store.connection as FakeApiConnection;
+      final stream = eg.stream();
+      connection.prepare(json: SendMessageResult(id: 12345).toJson());
+      await store.sendMessage(
+        destination: StreamDestination(stream.streamId, 'world'),
+        content: 'hello');
+      check(connection.lastRequest).isA<http.Request>()
+        ..method.equals('POST')
+        ..url.path.equals('/api/v1/messages')
+        ..bodyFields.deepEquals({
+          'type': 'stream',
+          'to': stream.streamId.toString(),
+          'topic': 'world',
+          'content': 'hello',
+          'read_by_sender': 'true',
+        });
+    });
+  });
+
   group('UpdateMachine.registerNotificationToken', () {
     late UpdateMachine updateMachine;
     late FakeApiConnection connection;