Outlook Not Syncing? 9 Fixes That Actually Work

Quick Fix

If Outlook is not syncing, the fastest fix is to press F9 (or click Send/Receive All Folders) to force a manual sync, then confirm you are online by toggling Work Offline off under the Send/Receive tab. If that fails, restart Outlook and check that your internet connection is stable. Nine times out of ten, a forced sync plus a restart clears a stuck mailbox.

Understanding the Outlook Not Syncing Problem

When Outlook stops syncing, new emails do not arrive, sent messages stay stuck in the Outbox, and your calendar or contacts fall out of date across devices. This happens because Outlook keeps a local cached copy of your mailbox (an OST or PST file) and periodically reconciles it with the mail server. If that reconciliation breaks, the local copy and the server drift apart.

The most common causes are a poor or interrupted internet connection, Outlook being switched to Work Offline mode, an oversized or corrupted data file, outdated credentials after a password change, or an add-in that interferes with the sync engine. On Microsoft 365 and Exchange accounts, server-side throttling or a temporary outage can also stall sync.

Because there are several moving parts, it helps to work through the fixes below in order, from the quickest to the most involved.

Method 1: Force a Manual Send/Receive

1. Open Outlook and click the Send/Receive tab.
2. Click Send/Receive All Folders (or press F9).
3. Watch the status bar at the bottom for “Updating Inbox” and wait for it to finish.

Method 2: Turn Off Work Offline

1. Go to the Send/Receive tab.
2. Look at the Work Offline button. If it is highlighted, click it once to go back online.
3. Check the bottom-right of the window. It should say “Connected” rather than “Working Offline”.

Method 3: Check Your Internet Connection

Open a browser and load any website. If pages will not load, restart your router and reconnect. On a corporate network or VPN, disconnect and reconnect the VPN, since a dropped tunnel often blocks Outlook from reaching the mail server even when web browsing still works.

Method 4: Restart Outlook and Your Computer

1. Close Outlook completely. On Windows, open Task Manager, find any outlook.exe process, and end it.
2. Reopen Outlook and let it run a full sync.
3. If it still stalls, restart the whole computer to clear background processes holding the connection.

Method 5: Update Outlook

An outdated build can break sync after a server change. Go to File > Office Account > Update Options > Update Now and install any pending updates. Restart Outlook afterward.

Method 6: Re-enter Your Account Password

If you recently changed your email password, Outlook may be silently failing to authenticate. Go to File > Account Settings > Account Settings, select your account, click Repair, and follow the prompts to sign in again.

Method 7: Rebuild the OST Data File

A corrupted cached file is a frequent culprit on Exchange and Microsoft 365 accounts. Outlook can rebuild it automatically:

1. Close Outlook.
2. Press Windows + R, type %localappdata%\Microsoft\Outlook, and press Enter.
3. Rename your account’s .ost file to something like old.ost.
4. Reopen Outlook. It will download a fresh copy of your mailbox from the server.

Method 8: Disable Problematic Add-ins

1. Go to File > Options > Add-ins.
2. At the bottom, set Manage: COM Add-ins and click Go.
3. Uncheck all add-ins, click OK, and restart Outlook.
4. If sync returns, re-enable add-ins one at a time to find the offender.

Method 9: Repair Your Office Installation

If nothing else works, repair Office itself. Open Settings > Apps > Installed apps, find Microsoft Office or Microsoft 365, choose Modify, then run a Quick Repair first and an Online Repair if needed.

Preventing Future Issues

• Keep Outlook and Windows updated so sync stays compatible with server changes.
• Archive old mail regularly to keep your data file small and responsive.
• Avoid running multiple email clients against the same account at once.
• Update Outlook immediately after any email password change.
• Use a stable, wired connection when downloading large mailboxes for the first time.

FAQ

Why is my Outlook inbox not updating but webmail works?

That usually means the local cached file or your stored credentials are out of date. Force a Send/Receive, re-enter your password via Account Settings, and if needed rebuild the OST file.

How do I force Outlook to sync immediately?

Press F9 or click Send/Receive All Folders on the Send/Receive tab. This triggers an immediate reconciliation with the server.

Does deleting the OST file delete my emails?

No. For Exchange and Microsoft 365 accounts your mail lives on the server, so deleting or renaming the OST simply forces Outlook to download a fresh copy. Never delete a PST file the same way, since PST data is stored only locally.

Why is my Outlook stuck on “Updating Inbox”?

This points to a large mailbox, a slow connection, or a corrupted item. Let it run, switch to a faster network, or rebuild the OST file if it never completes.

Could an add-in stop Outlook from syncing?

Yes. Faulty COM add-ins can interfere with the sync engine. Disable all add-ins, confirm sync works, then re-enable them one by one.

How often does Outlook sync automatically?

By default Outlook syncs every few minutes when connected, but you can adjust the schedule under Send/Receive > Send/Receive Groups > Define Send/Receive Groups.