For a while now, my sent mail folder has been over/underactive. For over a decade, I've bcc'd myself on emails and handled the incoming bcc from the inbox. This meant I deleted the sent mailbox without concern.
The account I have a problem with is a google apps for domains
Recently, though, Mavericks mail has both funneled some of my BCCs into the sent folder (sporadically, the worst kind of error) and linked other messages in the inbox to the versions displayed in the sent folder. Trashing the message in the sent folder leads to deleting the inbox version as well as any version that I moved to a different folder.
Since this started, I haven't deleted any of those sent messages, which is possibly just an annoyance and kludge rather than a life-threatening disorder, but still.
I've tried tweaking the gmail folder settings, but no changes in behavior have been observed.