ISSUE:
Multiple Draft Versions of Composed Message Ends Up In Trash Folder
While Composing a new message from a Gmail IMAP account in Mavericks Mail, if you leave the message you are composing open for any period of time (for example the period of time it takes to write an email) you will find multiple copies of the Draft version of that message in the Trash folder in the Gmail web client. Granted, Trash is trash, however it makes finding something in there when browsing the list of items very difficult. I remember the same issue with Mountain Lion that was fixed at some point in an update.
AND IT GETS BETTER:
Remembering the fix for this issue is to uncheck the option under Mailbox Behaviors for "Store Draft Messages on the Server" (which then just stores drafts locally on the Mac and avoids the issue of lots of Draft messages ending up in your Trash folder) - I tried unchecking the box and then closing the dialog box - I was presented with a Are You Sure - Save / Cancel...I clicked Save. Went back into the Preferences and the option was still checked. Exiting and relaunching Mail has no effect to make the setting stick.
The person in charge of the Apple Mail Quality Assurance (QA) Team should be fired. Immediately.