diff --git a/backend/demo/src/main/resources/contents.json b/backend/demo/src/main/resources/contents.json
index 03a7c033a1..5443d1871f 100644
--- a/backend/demo/src/main/resources/contents.json
+++ b/backend/demo/src/main/resources/contents.json
@@ -2,7 +2,7 @@
   "inbox": {
     "name": "Inbox",
     "type": "INBOX",
-    "messageServerIds": ["intro", "many_recipients"]
+    "messageServerIds": ["intro", "many_recipients", "thread_1", "thread_2"]
   },
   "trash": {
     "name": "Trash",
diff --git a/backend/demo/src/main/resources/inbox/thread_1.eml b/backend/demo/src/main/resources/inbox/thread_1.eml
new file mode 100644
index 0000000000..a597808451
--- /dev/null
+++ b/backend/demo/src/main/resources/inbox/thread_1.eml
@@ -0,0 +1,9 @@
+MIME-Version: 1.0
+From: Alice <alice@k9mail.example>
+Date: Fri, 10 Feb 2023 10:00:00 +0100
+Message-ID: <thread-1@k9mail.example>
+Subject: Thread
+To: Bob <bob@k9mail.example>
+Content-Type: text/plain; charset=UTF-8
+
+This is the first message in this thread.
diff --git a/backend/demo/src/main/resources/inbox/thread_2.eml b/backend/demo/src/main/resources/inbox/thread_2.eml
new file mode 100644
index 0000000000..5b455009b8
--- /dev/null
+++ b/backend/demo/src/main/resources/inbox/thread_2.eml
@@ -0,0 +1,11 @@
+MIME-Version: 1.0
+From: Bob <bob@k9mail.example>
+Date: Fri, 10 Feb 2023 10:05:00 +0100
+Message-ID: <thread-2@k9mail.example>
+Subject: Re: Thread
+To: Alice <alice@k9mail.example>
+In-Reply-To: <thread-1@k9mail.example>
+References: <thread-2@k9mail.example>
+Content-Type: text/plain; charset=UTF-8
+
+This is the second message in this thread.