diff --git a/server/src/scripts/determine-sender-status.js b/server/src/scripts/determine-sender-status.js
new file mode 100644
index 000000000..df12bca8c
--- /dev/null
+++ b/server/src/scripts/determine-sender-status.js
@@ -0,0 +1,56 @@
+// @flow
+
+import { messageSpecs } from 'lib/shared/messages/message-specs';
+import { messageTypes } from 'lib/types/message-types';
+import { updateTypes } from 'lib/types/update-types';
+
+import { createUpdates } from '../creators/update-creator';
+import { dbQuery, mergeOrConditions, SQL } from '../database/database';
+import { main } from './utils';
+
+async function determineSenderStatus() {
+  const includedMessageTypes = Object.keys(messageTypes)
+    .map((key) => messageTypes[key])
+    .filter((type) => messageSpecs[type].includedInRepliesCount);
+
+  const sendersQuery = SQL`
+    SELECT DISTINCT m.thread AS threadID, m.user AS userID
+    FROM messages m 
+    WHERE m.type IN (${includedMessageTypes})  
+  `;
+  const [senders] = await dbQuery(sendersQuery);
+
+  const conditions = senders.map(
+    ({ threadID, userID }) => SQL`thread = ${threadID} AND user = ${userID}`,
+  );
+  const setSenders = SQL`
+    UPDATE memberships m
+    SET m.sender = 1
+    WHERE 
+  `;
+  setSenders.append(mergeOrConditions(conditions));
+
+  const updatedThreads = new Set(senders.map(({ threadID }) => threadID));
+  const affectedMembersQuery = SQL`
+    SELECT thread AS threadID, user AS userID
+    FROM memberships
+    WHERE thread IN (${[...updatedThreads]})
+      AND role >= 0
+  `;
+
+  const [[affectedMembers]] = await Promise.all([
+    dbQuery(affectedMembersQuery),
+    dbQuery(setSenders),
+  ]);
+
+  const time = Date.now();
+  const updates = affectedMembers.map(({ threadID, userID }) => ({
+    userID,
+    time,
+    threadID,
+    type: updateTypes.UPDATE_THREAD,
+  }));
+  await createUpdates(updates);
+}
+
+main([determineSenderStatus]);