Common problems

Outlook stays on "Synchronizing subscribed folders" for hours

When you add a large mailbox to Outlook, the progress window may show "Synchronizing subscribed folders" for hours. This is usually the first sync, which only happens once.

Updated November 2026 All common problems Manuals Support
On this page
  1. What you see
  2. Why it happens
  3. What to do
  4. When to contact support

What you see

After you add the account, the Outlook Send/Receive Progress window appears. It shows Synchronizing subscribed folders for ana@navarra.com.br, with a progress bar. The bar moves slowly and sometimes goes back to the start and restarts the same folder.

Meanwhile, folders appear and messages arrive little by little.

Why it happens

On your computer, Outlook uses an IMAP account. During the first sync, it downloads the messages in every subscribed folder to your computer, one folder at a time. That's why:

  • A large mailbox takes time. A mailbox with several GB and dozens of folders can take hours, depending on your internet speed.
  • A folder may start over if the connection drops or the computer goes to sleep. That's why the progress seems to go back to the start.
  • After the first time, it's fast. On later syncs, Outlook only fetches what changed.

What to do

  1. Leave Outlook open until it finishes. Use a stable network and set your computer not to go to sleep during the sync. Ideally, let it run overnight or at a time when you're not using the computer.
  2. Unsubscribe from the folders you don't use in Outlook. In the folder list, under Mail, right-click the account name (your email address) and choose IMAP Folders. Click Query, select the folder and click Unsubscribe. To select several, hold down the Ctrl key. The folders stay on the server and in webmail; Outlook just stops downloading them. If you change your mind, use Subscribe in the same window. These names are from classic Outlook (Microsoft 365, 2021 and 2024). In the new Outlook, the steps are different.
  3. Clean up old folders in webmail. Folders that came from a migration tend to be many and rarely used. Combine the messages into fewer folders in webmail and then unsubscribe from the folders that are now empty.
  4. If you can't wait, look up older messages another way. On your phone, add the mailbox as an Exchange account (see On your phone, use an Exchange account). To read older messages, use webmail, which doesn't download anything to your computer.

Microsoft doesn't document a way to limit how far back Outlook downloads messages for IMAP accounts. That's why the steps above focus on subscribed folders and on waiting.

Are you using the new Outlook and your account does not connect or does not sync? For lua.email accounts, we recommend classic Outlook. See The new Outlook does not connect or does not sync your account.

When to contact support

Contact our team if:

  • the sync never finishes, even after leaving Outlook open all night;
  • errors show up on the Errors tab of the progress window;
  • Outlook keeps asking for your password. First, check that you're using your app password, which is different from your webmail password: see App password and Your password is rejected.

To speed things up, include your email address (never your password), what you tried, the exact error message and the approximate date and time. See the channels on Support.

See also