Hi Mo8888,
Welcome to post in Outlook forum. Before we go on, could you please clarify the following questions so that our forum members can help you better?
1. What's the type of your account? You may check the account type via File > Account Settings > Account Settings.
2. Is there any error message when the problem occurs? Or do you mean the messages are stuck in the Outbox?
3. What steps you have tried so far to try solving the issue?
If you see messages piling up in your Outlook outbox, please check the bottom of Outlook window and make sure Outlook is connected to the email server.
Besides, please check if the message stuck in the Outbox contains a large attachment. As some email providers has limitation on the size of the outgoing messages.
Additionally, you may refer to the article below for more possible solutions:
My messages won't send
Hope you can find this helpful. If you get any update from the ticket you opened, it is also appreciated that you can post back to share with us.
Regards,
Yuki Sun
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