If you are facing the issue in the sent box of your Outlook that it is not sending messages without showing any error, do not worry. The matter is in that loop, but after this execution, the mails sending process doesn’t trigger. All other arguments are also correct and mapped aptly but the last step of send is not working.
In this situation, ensure that your outlook is online.
Check if emails in outlook are in sending process. If the number of emails is large, the program is trying to update the emails and not sending them. So, try sending one by one or two by two.