Drag and drop is exactly what I've attempted. For the sent items I received an error right away and no messages were copied/moved. For the "other" folder it started copying and then produced an error after about 20 messages.

I'm trying again right now and will post back any error messages I receive.

Got an error after about 70 messages but it was dismissed quickly as I was in the middle of something else. Something about not being able to write to the folder though.

I started again with the remaining messages and so far it's up to 90-something (checked through Mail's Activity window)


The other issue I'm having right now is that when I reply to email in this imap enabled account on my desktop, instead of sent mail going to the sent mail folder on the server, it's going to a local folder. Even if I delete the local folder it just gets recreated after an additional reply. Arrgh. And YES, the "Store sent messages on the server" option is checked in the settings for that account.

SOLVED. The Mac client was using a different sent folder than the iPhone. Arrgh. On the iPhone you can set which folder to use for sent items. So I used the existing 'Sent' folder. The Mac client on the other hand was using "Sent Messages" by default.