How to fix macOS Mail app stuck on 'Downloading Messages' or failing to sync

Summary

This guide helps you troubleshoot and resolve: How to fix macOS Mail app stuck on 'Downloading Messages' or failing to sync. Follow the steps below to fix the issue.

Common Causes

It can be frustrating when the macOS Mail app hangs on the "Downloading Messages" status or fails to sync your latest emails. This issue is often caused by a corrupted local index, a stalled connection to the mail server, or an authentication glitch. This guide will walk you through the steps to resolve these sync issues and get your inbox flowing again.

Quick Fix Steps

Before attempting more complex solutions, try these basic troubleshooting steps to rule out simple connectivity or software glitches:

• Restart the App: Fully quit Mail by pressing Command + Q and then relaunching it.
• Check Internet Connectivity: Ensure your Mac is connected to a stable network. Try loading a webpage in Safari to verify.
• Check System Status: Ensure your mail provider (e.g., Microsoft 365, Google Workspace) isn't experiencing a service outage.
• Toggle Online Status: Go to the Mailbox menu and select Take All Accounts Online if they have been accidentally taken offline.

Detailed Instructions

Method 1: Force a Re-sync using the Mailbox Menu

Sometimes the app simply needs a manual nudge to reconnect with the server.

1. Open the Mail app.
2. Select the account that is stuck in the sidebar.
3. Click on the Mailbox menu in the top menu bar.
4. Select Get All New Mail.
5. If the messages are still not appearing, select Synchronise from the same menu.

Method 2: Re-authenticate the Account

Sync issues are frequently caused by expired passwords or token timeouts, even if the app isn't explicitly asking for a password.

1. Click the Apple Menu () and select System Settings (or System Preferences on older macOS versions).
2. Navigate to Internet Accounts.
3. Select the problematic email account from the list.
4. If you see a message saying "Account Password Required," click the prompt to re-authenticate.
5. If no prompt is visible, toggle the Mail switch Off, wait 10 seconds, and toggle it back On.

Method 3: Rebuilding the Mailbox

If the app is stuck "Downloading Messages" but you can see the emails via webmail, your local index may be corrupted. Rebuilding the mailbox forces Mail to re-download the index from the server.

1. In the Mail app, select the folder that is not syncing (e.g., Inbox).
2. Click on the Mailbox menu in the top menu bar.
3. Select Rebuild at the bottom of the dropdown menu.
4. Note: The mailbox may appear empty for a few minutes while it re-indexes. Do not close the app during this process.

Method 4: Removing and Re-adding the Account

If the above steps fail, removing the account entirely and adding it back is the most effective way to clear persistent configuration errors.

1. Go to System Settings > Internet Accounts.
2. Select the account and click Delete Account (or the minus − button).
3. Restart your Mac to ensure all cached session data is cleared.
4. Return to Internet Accounts and click Add Account.
5. Follow the prompts to sign back into your email service.

Troubleshooting Advanced Issues

Checking for Third-Party Interference

Certain security software or VPNs can interfere with the encrypted connection between macOS Mail and the mail server.

• VPNs: Disable any active VPN and check if the sync resumes.
• Firewalls/Antivirus: Temporarily disable third-party firewalls to see if they are blocking the mail ports (typically 993 for IMAP or 465/587 for SMTP).

Updating macOS

Apple frequently releases patches for the Mail app to ensure compatibility with evolving server security standards.

1. Go to System Settings > General > Software Update.
2. Install any available updates for macOS.
3. Restart your computer and test the Mail app again.

If you have followed these steps and your mail is still not syncing, please Open a Ticket so our technical team can analyse your account configuration.

Still Having Issues?