Why does Mail sometimes create drafts (and multiple drafts) for emails that are in fact sent already?  can I kill whatever feature that is? want to point me where to find the answer?

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This is a common issue but can be solved easily. It’s showing you the stored sent message on the server. The way to solve the issue is to go to mail’s preferences and select the account in question. Next, under “mailbox behaviors” unselect the checkboxes next to “store sent messages on server” and “store draft messages on server”. That should take care of it.