Updated: March 31, 2020

Having emails stuck in Outbox is a pretty common issue in Outlook: you’ve wrote an email, clicked to send it, but it stays in the Outbox folder and Outlook is not sending the email, no matter what you do. This article details possible causes & solutions and it applies to all Outlook versions, including Outlook 2019.
There can be many reasons why Outlook wouldn’t send an email. To narrow the cause of the Outbox stuck emails, first of all you should check if you receive an error message while you perform a Send / Receive operation.

If you receive an error message while you try to send the email

Most likely there is a communication problem between Outlook and your outgoing mail server, so the email is stuck in Outbox because Outlook can’t connect to your mail server to send it.
– check with your Internet service provider to make sure it doesn’t block the port number that you are using for the outgoing mail server (some providers block port 25 or other ports that may be used by an outgoing / SMTP mail server);
– check with your email address provider and make sure your mail server settings are up to date. Occasionally, mail server providers change port numbers or authentication methods, so even if your Outlook account used to send emails without any problems, it may not be working anymore because the outgoing mail server settings were changed;
– check with your email address provider and make sure you didn’t exceed the hourly / daily email send quota (or other send limits enforced by your email provider);
– if you are on a slow Internet connection, make sure your Outbox emails are not supposed to include very large attachments (10 – 20 Mb or more). The server connection may time out before Outlook gets to send a large email;
– if the above solutions don’t work, use Google and search for the exact error code that you received while you are trying to send the Outlook email: it will likely lead you to a precise solution. You should also check out this list of the most common send & receive error messages and their solutions.

If you do not receive an error message while you try to send the email

The problem is likely to be related to your local Outlook configuration.

If Outlook is not sending only some Outbox emails, make sure you don’t have the habit to preview / open / click on Outbox emails: your Outbox emails should be unread (marked with bold & italic) otherwise Outlook will not send the email and it will be stuck in your Outbox folder. Check your Outbox emails:
— if the email is bold and italic, then it is ready to be sent;
— if the email is just marked with bold, then it was read;
— if the email is not marked with bold or italic, then the email was read and edited. As in the following screenshot, only the first email (with the subject “Unread email”) is going to be sent by Outlook while the other emails will stay in the Outbox folder:
To re-arm an Outbox email, simply double click on it to edit it, then click again on the Send button.

Before clicking on the Send button, make sure you browse to a different Outlook folder, so you avoid automatically marking it again as read when you exit the email window.

If Outlook is not sending any of your Outbox emails and they are not marked as read (as above), then try one of the following solutions:
— make sure Outlook is not set to the Offline mode. You can check if Outlook is offline from the Send / Receive ribbon (toolbar) button:

— make sure you don’t have an over-zealous antivirus that scans your Outbox emails and prevents them from being sent. Do a simple test and disable your antivirus protection, restart Outlook and try to send the Outbox emails once again. If they get sent, configure your antivirus and prevent it from scanning Outbox emails.
— if your Outbox emails contain file attachments and you are using Outlook 2013 with iCloud or any other cloud storage service, make sure your file attachments are fully uploaded to your cloud account, before sending them;
— your Outlook data files might be corrupted: perform a data file scan using the Outlook ScanPST tool.

If you deal with emails stuck in your Outbox folder and you can’t fix Outlook using any of the above solutions, please feel free to post your comments below and we will gladly try to help you.

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