Outlook Outbox Folder Warning

This article provides a solution for the following Outlook warning message when you try to close the application:

The Outbox is a folder in Outlook that acts as a temporary storage space for emails that are being sent by Outlook. When you send an email it goes from Draft --> Outbox --> Sent Items. The above error is when it cannot get to Sent Items

The most common cause of this is that you tried to send an email message. Even if you were connected to the internet at the time, Outlook has a Work Offline mode that, while rare, sometimes uses if the internet connection had a brief disruption. You can always tell by the small red X circle on the Outlook icon

Another cause may be the size of a message. By default Outlook will only allow you to send an email if the total combined size of the email is >=20mb, including the text itself in addition to the attachments

There are 2 main solutions to fix this

Solution #1 - Send & Receive All Folders

If your Outlook is online (without the red circle on the icon) then there is an option available to force Outlook to Send and Receive all mail in each one of the Mailboxes you currently have on your Outlook (make sure Work Offline button is NOT highlighted too)

This 'kick' to Outlook may get it to try to send the items in the Outbox and provided the messages are not too large they should move to your sent items

Solution #2 - Empty your Outbox

If the items are too large / they are still not moving to your sent items you may have to look at removing your Outbox items. This can be done 1 by 1 by highlighting the mail and deleting or this can be done for the entirety of the mailbox

If you are concerned about finding a way to share larger files with external users please see below guide in which you can create an individual access link to a document/folder in SharePoint Online. This is also applicable to internal users but should only be used under specific circumstances when they cannot directly access where the file/folder is stored

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