Outlook for Mac Email Stuck in Outbox? Here’s How to Fix It

Are your emails stuck in the Outbox? If yes, you are not alone. It is one of the most frustrating but common issues. It is one of the most reported issues among Mac users while running MS Outlook. What the query – Outlook for Mac Email Stuck in Outbox indicates is that Outlook is unable to send the messages to the mail server due to some connectivity or other software-related issues. We are listing out all the causes that lead to this issue and how we can overcome them without losing any data.

In the guide, you will get the causes and the respective working fixes from quick to advanced solutions. Go through each of the methods one by one, get emails out of the Outbox, and complete the send process.

What is the Use of the Outbox in Outlook?

Outbox in Outlook is used to handle the message sending process. It gives Outlook a place for the emails to queue before they are delivered. It works when you are offline; that is, emails stay in the Outbox and are sent automatically once you are back online. We can edit or delete it before sending it from the Outbox folder. If you want to send multiple emails, they will be queued in the Outbox and sent one by one.

Why is Your Outlook for Mac Email Stuck in Outbox?

Before we go to the fixes, understand what is causing the issues. Outlook for Mac queues the emails in the Outbox while the email account establishes a server connection and then sends the messages.

When the messages get stuck there, that means something has intercepted the transmission and blocked the process. Here are some common causes: Outlook Mac emails stay in the Outbox.

• The server sets a limit on the size of the attachments; if the files are too big, then the message will fail.
• If the message is corrupted, Outlook won’t be able to handle it effectively.
• Going offline/unstable internet connection during the process of transferring the emails.
• Authentication failure, e.g., Wrong password or expired OAuth token.
• Incorrect or outdated outgoing mail server configurations (SMTP).
• Offline mode is enabled accidentally and not going back to online – check the article: Outlook Stuck in Offline Mode
• Outdated Outlook might have some bugs.
• Antivirus or firewall software is blocking Outlook’s outbound connections.

Pro Tip: If messages are unable to send and remain pending in the Outbox, other reason could be connection issue with the server. Check out the solutions to fix Outlook disconnected from Exchange Server.

How to Fix the “Outlook Mac Emails Stuck in Outbox” – Quick Checks First

First, we will go through some quick solutions before we move on to advanced fixes. Many stuck emails and Outlook issues are resolved mostly with these steps:

Check Internet Connection

Open Safari or Chrome and visit any webpage. The internet is not the issue. If not, troubleshoot the network; Outlook cannot proceed with sending the emails without an internet connection.

Check whether Outlook is in Offline Mode

Mac Outlook can sometimes be in offline mode due to various reasons.

1. Open Outlook for Mac.
2. Look at the menu bar and click on Outlook.
3. Check for Work Offline in the dropdown menu.
4. Click on Work Offline to remove it.
5. Confirm Outlook is back online.

Advanced Fixes to Resolve “Outlook Emails Stuck in Outlook” Error

Fix 1: Delete and Resend the Stuck Emails

Start with the simple fix by deleting the stuck message and composing a fresh one:

1. Open Outlook for Mac, click on “Outbox” in the left panel.
2. Right-click the message and select the Delete option from the menu.
3. If the message is not deleted, try switching to offline first and deleting it. Then go back online.
4. Compose a new email and attempt to send it.

If the new message is sent successfully, the original message was corrupted. If the message is stuck again in the Outbox, then the issue is systemic and requires more technical fixes.

Fix 2: Reduce the Email Attachment Size

The common reason emails get stuck in the Outbox is the attachment size. If the attachments exceed the maximum allowed size by the mail server or Microsoft 365 policy.

• Microsoft 365 has a default maximum size of 25 MB.
• An on-premises Exchange server has a limit set by organisation configuration: 10-35 MB.
• A Gmail account configured in Outlook imposes a 25 MB limit.

How to fix “Outlook for Mac Email Stuck in Outbox” by compressing attachments:

1. Remove the stuck email from the Outbox.
2. Full attachment – right-click > Compress in Mac.
3. If they are still too large, share them with OneDrive, Google Drive, SharePoint, or Dropbox.
4. Attach the file as a hyperlink directly into the body of the email.
5. Resend the email.

Fix 3: Force Outlook to Send via Offline Mode

Allows you to try to re-send a message placed in the queue by switching the offline state:

1. Click the Outlook menu and select Work Offline.
2. Hold on for a few seconds.
3. Repeat the step from the Outlook menu > Work Offline.
4. Outlook will try to send the Outbox message right away.

Works most of the time as it restarts Outlook’s connection to the mail server, thereby breaking any temporary connection hang that is preventing the send.

Fix 4: Update the Mac Outlook Application to Fix “Outlook for Mac Email Stuck in Outbox”

The Outbox issue is caused by bugs in older versions of Outlook that Microsoft has since patched. Keep Outlook updated to fix and prevent any issues in the future.

• Open the MS Office application.
• Go to the Help menu at the top.
• Click “Check for Updates”
• The Microsoft AutoUpdate tool will open and scan for any updates.
• Click “Update All” and allow the installation to complete.
• Relaunch Outlook after the update and check whether the Outbox issue is resolved.

If there is no “Check for Updates” in the Help menu, you may have installed Outlook from the Mac App Store.

Fix 5: Rebuild Outlook Profile

This is a very common cause of emails being stuck in the Outbox, but one that often goes unnoticed. Rebuilding the profile causes Outlook to reconnect to the accounts from scratch.

1. Close Outlook completely.
2. Open Finder: ~/Library/Group Containers/UBF8T346G9.Office/Outlook/Outlook 15 Profiles
3. Now, you need to right-click your current profile folder and change its name.
4. Relaunch Outlook, and a new profile will be created.
5. Enter your account information and let Outlook synchronise.

Rebuilding the profile does not delete the emails if you use Exchange, Microsoft 365, IMAP, or Gmail – they will resync from the server.

Tip: Locally stored items in the On My Mac folder will not be in the new profile. So make sure to back it up first. You can export your data using Outlook’s built-in export feature or use the Email Backup Tool to save all the important emails before rebuilding the Outlook profile.

Fix 6: Verify and Correct SMTP Outgoing Mail Server Settings

If the SMTP setting is incorrect in the email account, then no messages will be sent from Outlook, and the email may remain stuck in the Outbox. This is particularly likely to occur if you have recently changed your password, have changes to your IT policy or are setting up a new account.

1. In Outlook, click on the Outlook menu, then select Preferences, and then Accounts.
2. Choose the email account that has a message pending in the Outbox.
3. Press Advanced or the settings icon.
4. Verify that the following Outgoing Mail Server (SMTP) settings are correct:
   • Enter the address for the server, as given by our email host.
   • Port: normally 587 (TLS) or 465 (SSL) — avoid port 25 as many ISPs block it.
   • Authentication: match the account type.
   • SSL/TLS: should be equivalent to the server requirement
5. Change the email password as well if you changed it recently.
6. Click OK, then try to send a test email.

Fix 7: Sign Out and Sign In to the Account

Microsoft 365 and Exchange account, the authentication token can expire, causing issues, including email send failures that appear in the Outbox. Sign out and sign back in, as it refreshes the token.

• In Outlook, go to the Outlook menu > Preferences > Accounts.
• Select Microsoft 365 or Exchange account
• Click on the minus (-) button to remove the account.
• Click the remove.
• Click the plus (+) button to add the account back.
• Enter the email address and follow the authentication instructions.
• Allow Outlook to complete the sync and test sending again.

Fix 8: Check Antivirus and Firewall Settings

Outbound emails can get stuck in your Outlook Outbox because some of your network security software blocks Outlook’s outbound connection on Port 587 or 465.

How to check:

1. Switch off Antivirus or Firewall software temporarily.
2. Open your Outlook & try sending one test email.
3. If it is successfully sent, then there is some problem with Antivirus / Firewall.
4. Re-open them and try adding Outlook to Trusted Apps or exceptions.

Fix 9: Clear Outlook Cache to resolve “Outlook for Mac Emails Stuck in Outbox”

Outlook saves local copies of the account data, messages, calendar, etc. If the cache gets corrupted, it may cause items to get stuck in the Outbox. Clear the Cache(s) as a forced sync to fresh.

1. Close Outlook completely.
2. Open Finder, select Go from the menu, press and hold the Option key, and select Library.
3. Go to: ~/Library/Caches/com.microsoft.Outlook.
4. Select the files in the folder and move them to the bin.
5. Go to: ~/Library/Containers/com.microsoft. Outlook/Data/Library/Caches
6. Delete the files.
7. Relaunch Outlook, then test by sending emails.

Fix 10: Finally, Remove and Reinstall Outlook for Mac

If none of the above fixes worked, then begin again by performing a clean reinstall of Outlook. It would solve any application-level problem that cannot even be fixed by the above-mentioned fixers.

1. Close the Outlook application.
2. Drag the Microsoft Outlook icon to the Trash, and empty the Trash.
3. Reboot the Mac to delete the Temp files.
4. Get the latest version of Outlook and download it from the official Microsoft site, and then install it through the Mac App Store.
5. Launch Outlook and log in to the account.
6. Wait for Outlook to complete its synchronisation, then attempt to resend the messages.

Close Outlook and then completely reset it to remove any problems that cause messages to be frozen in the Outbox.

FAQs

Q) Why are they in the Outbox and not found in the Sent Items?

A) This indicates Outlook tried to send the message but did not get the delivery confirmation from the server. This message is in the Outbox as Outlook keeps trying.

Q) Is there a way I can access and make changes to the stuck message that is currently located in the Outbox?

A). Yes. Double-click each message as it is stored in the Outbox. This will open a window where your message can be amended. You can edit your messages, remove attachments, or change the recipients. Once amended, click Send again. However, this might not work for some versions and must be done while Outlook is offline.

Q) Can we forcefully push the Outlook messages at once?

A) Yes. Select the Outlook menu> Work Offline, switch on Offline mode, wait a couple of seconds, and then switch off Offline mode. It forces Outlook to flush and try to send the messages at the same time.

Conclusion

Outlook for Mac emails stuck in Outlook are not a data loss scenario. If an email gets stuck, there is nothing wrong with that — it is mostly due to issues with connectivity/authentication/setup issues, which can be rectified without impacting the messages. First, do the fundamentals, like check if you are actually online and not working offline. If not, then get the available solutions in order of least effort to greatest effort. Delete the single stuck message and re-send its contents – reconfigure your SMTP settings or resynchronise with your authentication server and reauthorise, reinstall the application and all associated components. Save critical attachments or email content before making any changes: you can do this with Outlook’s own backup/export feature, or a specialised utility. Once you’re finished, your Outbox should be empty again and your queue clear-reason restored.