Sent messages are stored on Exchange server as draft
I am using Thunderbird 102.7.1 on Ubuntu 22.04. My work email address is on an what I'm pretty sure is an Exchange server (https://outlook.office365.com/EWS/Exchange.asmx) and I sometimes access this email through a Windows computer running Outlook, or through the webmail interface at outlook.office.com/mail, or through the Gmail app on Android.
When I send messages from Thunderbird, the configuration is to "place a copy in "Sent" folder on firstname.lastname@example.org on outlook.office365.com"
However, when I use Outlook or webmail or my phone, the copy is marked as a draft. Any thoughts on why this might be?
It makes things difficult as I can be unsure about whether I really did send the email and I also cannot reply to emails I have sent, so it is hard to maintain good threading of my email.