Yes - I'm having the same issue. On top of that, the emails which haven't been sent and are sitting in drafts and appearing and disappearing, e.g. the drafts folder is showing that there are 11 drafts, but only actually showing 8 of them in the folder when you click into it. I have to click out of drafts and back in to see them all, and quote often some of them are disappearing in front of my eyes (so I click out and back in again and open the draft email as quickly as I can)!
I am having to watch each and every email go out (i.e. watching the drafts folder to make sure it goes from 1 to 0 when I press send, and then give it a few seconds because sometimes it goes back into drafts after it's "sent". Then I go into sent items to check it's actually gone.
The only way I can get these "stuck" emails out is to right click on them in the Drafts folder, choose forward and forward on to the original recipient and then delete the "stuck" draft. Incredibly tedious and time consuming.
It looks like this has been an issue for some time - what the heck of Microsoft doing (or not doing!)?! Ridiculous.