Emails are not sent from the Outlook inbox if Send immediately when connected has not been set
If Outlook is configured in such a way that emails remain in the outbox after clicking on Send immediately when connected, a problem can occur if you look at the email again before the fact. In this case, the email is returned to draft mode and must be returned to send mode by clicking Send again before it can be sent.
This is not a specific behaviour with the Outlook Add-in, but a general Outlook behaviour.