diff --git a/packages/isomorphic-core/src/imap-connection.js b/packages/isomorphic-core/src/imap-connection.js
index f1ff3fffe..0a3286ea6 100644
--- a/packages/isomorphic-core/src/imap-connection.js
+++ b/packages/isomorphic-core/src/imap-connection.js
@@ -262,18 +262,18 @@ class IMAPConnection extends EventEmitter {
     }
 
     const {operation, resolve, reject} = this._currentOperation;
-    const result = operation.run(this._db, this);
-    if (result.constructor.name !== "Promise") {
+    const resultPromise = operation.run(this._db, this);
+    if (resultPromise.constructor.name !== "Promise") {
       reject(new Error(`Expected ${operation.constructor.name} to return promise.`))
     }
 
-    result.then(() => {
+    resultPromise.then((maybeResult) => {
       this._currentOperation = null;
       this._logger.info({
         operation_type: operation.constructor.name,
         operation_description: operation.description(),
       }, `Finished sync operation`)
-      resolve();
+      resolve(maybeResult);
       this.processNextOperation();
     })
     .catch((err) => {
diff --git a/packages/local-sync/src/local-api/routes/threads.js b/packages/local-sync/src/local-api/routes/threads.js
index 0daed2f4c..af793715f 100644
--- a/packages/local-sync/src/local-api/routes/threads.js
+++ b/packages/local-sync/src/local-api/routes/threads.js
@@ -1,4 +1,5 @@
 const Joi = require('joi');
+const stream = require('stream');
 const _ = require('underscore');
 const Serialization = require('../serialization');
 const {createSyncbackRequest} = require('../route-helpers')
@@ -69,8 +70,13 @@ module.exports = (server) => {
       const account = request.auth.credentials;
       const db = await request.getAccountDatabase();
       const client = searchClientForAccount(account);
-      const threads = await client.searchThreads(db, request.query.q, request.query.limit);
-      reply(`${JSON.stringify(threads)}\n`);
+      const source = await client.searchThreads(db, request.query.q, request.query.limit);
+
+      const outputStream = stream.Readable();
+      outputStream._read = () => { return };
+      const disposable = source.subscribe((str) => outputStream.push(str));
+      request.on("disconnect", () => disposable.dispose());
+      reply(outputStream);
     },
   });
 
diff --git a/packages/local-sync/src/local-api/search.js b/packages/local-sync/src/local-api/search.js
index 004e88713..3d2e1cfb9 100644
--- a/packages/local-sync/src/local-api/search.js
+++ b/packages/local-sync/src/local-api/search.js
@@ -1,9 +1,36 @@
 const request = require('request');
 const _ = require('underscore');
+const Rx = require('rx');
+const {IMAPConnection} = require('isomorphic-core')
+
+const getThreadsForMessages = (db, messages, limit) => {
+  const {Message, Folder, Label, Thread} = db;
+  const threadIds = _.uniq(messages.map((m) => m.threadId));
+  return Thread.findAll({
+    where: {id: threadIds},
+    include: [
+      {model: Folder},
+      {model: Label},
+      {
+        model: Message,
+        as: 'messages',
+        attributes: _.without(Object.keys(Message.attributes), 'body'),
+        include: [
+          {model: Folder},
+        ],
+      },
+    ],
+    limit: limit,
+    order: [['lastMessageReceivedDate', 'DESC']],
+  });
+};
 
 class GmailSearchClient {
-  constructor(accountToken) {
-    this.accountToken = accountToken;
+  constructor(account) {
+    const credentials = account.decryptedCredentials();
+    this.accountToken = account.bearerToken(credentials.xoauth2);
+    this.account = account;
+    this._logger = global.Logger.forAccount(this.account);
   }
 
   // Note that the Gmail API returns message IDs in hex format. So for
@@ -53,7 +80,7 @@ class GmailSearchClient {
         if (numTries >= maxTries) {
           // If we've been through the loop 10 times, it means we got a request
           // a crazy-high offset --- raise an error.
-          console.error('Too many results:', results.length);
+          this._logger.error('Too many results:', results.length);
           reject(new Error('Too many results'));
           return;
         }
@@ -112,39 +139,147 @@ class GmailSearchClient {
       return [];
     }
 
-    const {Message, Folder, Label, Thread} = db;
+    const {Message} = db;
     const messages = await Message.findAll({
       where: {gMsgId: {$in: messageIds}},
     });
 
-    const threadIds = _.uniq(messages.map((m) => m.threadId));
-    const threads = await Thread.findAll({
-      where: {id: threadIds},
-      include: [
-        {model: Folder},
-        {model: Label},
-        {
-          model: Message,
-          as: 'messages',
-          attributes: _.without(Object.keys(Message.attributes), 'body'),
-          include: [
-            {model: Folder},
-          ],
-        },
-      ],
-      limit: limit,
-      order: [['lastMessageReceivedDate', 'DESC']],
+    const stringifiedThreads = getThreadsForMessages(db, messages, limit)
+      .then((threads) => `${JSON.stringify(threads)}\n`);
+    return Rx.Observable.fromPromise(stringifiedThreads);
+  }
+}
+
+class SearchFolder {
+  constructor(folder, criteria) {
+    this.folder = folder;
+    this.criteria = criteria;
+  }
+
+  description() {
+    return 'IMAP folder search';
+  }
+
+  run(db, imap) {
+    return imap.openBox(this.folder.name).then((box) => {
+      return box.search(this.criteria);
+    });
+  }
+}
+
+class ImapSearchClient {
+  constructor(account) {
+    this.account = account;
+    this._conn = null;
+    this._logger = global.Logger.forAccount(this.account);
+  }
+
+  async ensureConnection() {
+    if (this._conn) {
+      return await this._conn.connect();
+    }
+    const settings = this.account.connectionSettings;
+    const credentials = this.account.decryptedCredentials();
+
+    if (!settings || !settings.imap_host) {
+      throw new Error("ensureConnection: There are no IMAP connection settings for this account.");
+    }
+    if (!credentials) {
+      throw new Error("ensureConnection: There are no IMAP connection credentials for this account.");
+    }
+
+    const conn = new IMAPConnection({
+      db: this._db,
+      settings: Object.assign({}, settings, credentials),
+      logger: this._logger,
+    });
+
+    this._conn = conn;
+    return await this._conn.connect();
+  }
+
+  closeConnection() {
+    if (this._conn) {
+      this._conn.end();
+    }
+  }
+
+  async _search(db, query) {
+    await this.ensureConnection();
+
+    // We want to start the search with the 'inbox', 'sent' and 'archive'
+    // folders, if they exist.
+    const {Folder} = db;
+    let folders = await Folder.findAll({
+      where: {
+        accountId: this.account.id,
+        role: ['inbox', 'sent', 'archive'],
+      },
+    });
+
+    const accountFolders = await Folder.findAll({
+      where: {
+        accountId: this.account.id,
+        id: {$notIn: folders.map((f) => f.id)},
+      },
+    });
+
+    folders = folders.concat(accountFolders);
+
+    const criteria = [['TEXT', query]];
+    return Rx.Observable.create((observer) => {
+      const chain = folders.reduce((acc, folder) => {
+        return acc.then((uids) => {
+          if (uids.length > 0) {
+            observer.onNext(uids);
+          }
+          return this._searchFolder(folder, criteria);
+        });
+      }, Promise.resolve([]));
+
+      chain.then((uids) => {
+        if (uids.length > 0) {
+          observer.onNext(uids);
+        }
+        observer.onCompleted();
+      }).finally(() => this.closeConnection());
+    });
+  }
+
+  _searchFolder(folder, criteria) {
+    return this._conn.runOperation(new SearchFolder(folder, criteria)).catch((error) => {
+      this._logger.error(`Search error: ${error}`);
+      return Promise.resolve([]);
+    });
+  }
+
+  async searchThreads(db, query, limit) {
+    const {Message} = db;
+    return (await this._search(db, query)).flatMap((uids) => {
+      return Message.findAll({
+        where: {
+          accountId: this.account.id,
+          folderImapUID: uids,
+        },
+      });
+    }).flatMap((messages) => {
+      return getThreadsForMessages(db, messages, limit);
+    }).flatMap((threads) => {
+      if (threads.length > 0) {
+        return `${JSON.stringify(threads)}\n`;
+      }
+      return '\n';
     });
-    return threads;
   }
 }
 
 module.exports.searchClientForAccount = (account) => {
   switch (account.provider) {
     case 'gmail': {
-      const credentials = account.decryptedCredentials();
-      const accountToken = account.bearerToken(credentials.xoauth2);
-      return new GmailSearchClient(accountToken);
+      return new GmailSearchClient(account);
+    }
+    case 'imap': {
+      return new ImapSearchClient(account);
     }
     default: {
       throw new Error(`Unsupported provider for search endpoint: ${account.provider}`);