Estimated Time to Fix: 5 minutes

Summary

If you are using a Mac and your Outlook inbox suddenly stops receiving new emails—while your phone or the web version of Outlook updates fine—the local app has likely lost its connection to the server. This guide covers how to force Outlook for Mac to reconnect and sync your mail.

Symptoms

• The status bar at the bottom of Outlook constantly says "Syncing..." but never finishes.
• New emails appear on your iPhone or the Outlook Web App, but do not show up on your Mac.
• Emails you send stay stuck in the "Outbox" folder.

Before You Start

• None required.

Instructions

1. Toggle "Work Offline" Mode

Often, Outlook gets stuck in a confused network state. Toggling its connection manually forces a reset.

1. Open Outlook on your Mac.
2. Look at the very top menu bar on your screen (next to the Apple logo) and click Outlook.
3. In the dropdown menu, see if Work Offline has a checkmark next to it. If it does, click it to uncheck it.
4. If it is not checked, click Work Offline to turn it on. Wait 10 seconds, then click it again to turn it back off.
5. Watch the bottom right corner of the Outlook window to see if it says "Connected" and begins downloading messages.
6. If the corner still reads "Syncing" a minute later, or reads "Connected" but no new mail arrives, the connection is fine and one folder's local copy is damaged. Continue to Step 2.

2. Empty the Cache for the Stuck Folder

If only one specific folder (like your Inbox or a Shared Mailbox) refuses to update, its local cache might be corrupted.

1. In Outlook, right-click (or Control + click) on the folder that is not syncing (e.g., Inbox).
2. Select Properties from the menu.
3. Click the Empty Cache button.
4. Click Empty to confirm.
5. The folder will temporarily appear empty while Outlook re-downloads everything directly from the Microsoft servers.
6. If the folder is still empty or still missing recent mail ten minutes later, the sync fault is in the version of the app you are running. Continue to Step 3.

3. Switch Between "New" and "Legacy" Outlook

Microsoft provides two entirely different versions of Outlook for Mac built into the same app. Switching between them often bypasses sync bugs.

1. Look at the top menu bar (next to the Apple logo) and click Outlook.
2. Look for the option that says New Outlook or Legacy Outlook.
3. If it has a checkmark, click it to uncheck it. If it doesn't, click it to check it.
4. Outlook will close and reopen in the other interface. Wait to see if your emails sync. You can switch back at any time.
5. If both interfaces stall at the same folder, the account is failing to sync rather than the app. Raise a ticket naming the folder that will not update, the date of the last email that did reach the Mac, and whether that same folder is up to date in Outlook on the web.

Troubleshooting

TIP

If your password recently expired and you changed it on your phone or online, Outlook for Mac might still be trying to use the old password in the background, causing a silent sync failure. You will need to update your password in the Mac's Keychain Access app.

Symptom / Error	Potential Cause	Solution
"Account Error" or triangle icon next to Inbox	Password issue	Click the triangle icon. You likely need to re-enter your Microsoft 365 password.
No emails are sending (stuck in Outbox)	Large attachment	An email with an attachment over 25MB is blocking the queue. Delete it from the Outbox.

Related Articles

• How to Fix Shared Mailboxes Not Updating in "New" Outlook
• Understanding Outlook Versions: Classic vs. New vs. Web

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