Send & Receive Issues

Fix Outlook 365 Emails Stuck in the Outbox

Elise Williams Oct 20, 2026 868 views

Question details

Users are experiencing issues where sent emails remain trapped in the Outlook Outbox and only transmit when manual sync is triggered.

How to Fix Outlook 365 Emails Stuck in the Outbox

Product: Microsoft Outlook 365
Device & OS: not provided
Scenario: Sending emails using the desktop client of Outlook 365.
Observed behavior: Emails fail to send automatically and stay stuck in the Outbox until the Send/Receive button is manually clicked. The issue persists even after repairing the profile or reinstalling the application.

Before you start

Verify that your computer has an active internet connection and check the bottom right corner of the Outlook window to ensure you are not currently in 'Working Offline' mode.

Solution 1Recommended

Configure Automatic Send/Receive Settings and Update Outlook

Ensure Outlook is configured to send emails immediately upon connection and that you are running the latest software version.

Often, Outlook messages remain in the Outbox because the automatic send/receive schedule has been disabled or corrupted. Updating the client can also resolve known synchronization bugs.

Modify Send/Receive Groups

Navigate to the 'Send / Receive' tab on the Outlook ribbon. Click on 'Send/Receive Groups' and select 'Define Send/Receive Groups' from the drop-down menu.

Enable Automatic Sync

In the dialog box, check the option for 'Schedule an automatic send/receive every [X] minutes' and ensure 'Perform an automatic send/receive when exiting' is also checked. Click 'Close'.

Update Microsoft 365

Go to 'File' > 'Office Account'. Under Product Information, click 'Update Options' and select 'Update Now' to download and install the latest Outlook patches.

Configure Automatic Send/Receive Settings and Update Outlook

Temporary Workaround: While troubleshooting, you can force emails in your Outbox to send by manually pressing F9 or clicking 'Send/Receive All Folders'.

Solution 2

Open a Microsoft 365 Service Request

Escalate the issue to Microsoft 365 Support if local desktop troubleshooting, such as creating new profiles or reinstalling, does not resolve the problem.

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Frequently Asked Questions

Why do my emails stay in the Outbox until I manually click Send/Receive?

This typically occurs if the 'Send immediately when connected' option in Outlook's advanced settings is unchecked, or if there is a corruption in your Send/Receive group configuration.

Will repairing my Outlook profile fix emails stuck in the Outbox?

Repairing or recreating an Outlook profile can resolve local file corruption. However, if the issue persists after creating a new profile, it is likely a server-side issue that requires a support ticket in the Microsoft 365 admin center.

Can a large attachment cause emails to get stuck?

Yes. If an email contains an attachment that exceeds the server's size limits (typically 20MB to 35MB), it may stall the entire synchronization process, trapping all subsequent emails in the Outbox.

How can I check if Outlook is working offline?

Look at the status bar at the very bottom of the Outlook window. If you see 'Working Offline' or 'Disconnected', go to the Send/Receive tab on the ribbon and click the 'Work Offline' button to reconnect.

Outlook & Email Problems