Why are all my "sent" emails ending up in Draft Folder?

This worked for one of my clients (windows 11)- if you go into your windows settings -> Apps -> Installed Apps -> then find "New Outlook" and click the three dots, select "advanced options". In that new page if you scroll down you have the options to "repair, reset, uninstall". All I had to do was the first repair and that fixed it, but if that doesn't work you could always try the other two. Just keep in mind that the reset and uninstall will remove the data tied to New Outlook and you'll need to perform some set up

I am using Windows 10 and tried to "repair" which didn't work for me. Too bad.

This issue just started happening for me this afternoon (at 11:33am I sent an email. At 12:49pm I tried to send another email and it both sent and appears to be in drafts). It's unclear which of my emails have actually sent and which are just drafts, as some of the "draft" emails have received replies. However, this is not occurring with every email I send, only some. It doesn't seem to matter if someone is in my address book or not. The status is consistent across platforms (a "draft" email is still a draft email when I open Outlook on my Mac) and I can't tell what has sent or not - at this point I am assuming that everything I tried to send has sent successfully. (I do have a 5 second delay set but it has been hours in some cases.)

I gave up and went back to the old MS Email.

MS folks don't seem interested and the recommended fixes do not work.

I too was having this issue. I have an M365 account and use the Outlook client installed app on my computer. My settings for "undo send" were set to 0 because I didn't want to do that. Messages sent showed in my sent folder and email string but the draft 'copy' stayed in my draft folder indefinitely until I manually deleted it. I set my undo setting to 5 seconds which resolved the issue. It is now working as expected (for enabling the undo option) but I would like to have the option to turn that feature off entirely.

Having the same problem!! Where is Microsoft staff? Why is no one addressing this issue? I have tried everything that has already been suggested and this continues.

Not only am I having the same issue, but I am having the issue with the legacy app (Version 16.89.3 (24092813).